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Sample records for diffuse in-stent restenosis

  1. Modelling and simulating in-stent restenosis with complex automata

    NARCIS (Netherlands)

    Hoekstra, A.G.; Lawford, P.; Hose, R.

    2010-01-01

    In-stent restenosis, the maladaptive response of a blood vessel to injury caused by the deployment of a stent, is a multiscale system involving a large number of biological and physical processes. We describe a Complex Automata Model for in-stent restenosis, coupling bulk flow, drug diffusion, and

  2. Randomized comparison between intracoronary β-radiation brachytherapy and implantation of paclitaxel-eluting stents for the treatment of diffuse in-stent restenosis

    International Nuclear Information System (INIS)

    Schukro, Christoph; Syeda, Bonni; Kirisits, Christian; Schmid, Rainer; Pichler, Philipp; Pokrajac, Boris; Lang, Irene; Poetter, Richard; Glogar, Dietmar

    2007-01-01

    Background and purpose: Intracoronary brachytherapy was the primary therapeutic option for the treatment of in-stent restenosis (ISR) during the last years. Especially for the treatment of diffuse ISR (lesions >10 mm), β-source brachytherapy was significantly superior to singular balloon angioplasty. Despite lacking clinical database, the implantation of drug eluting stents recently became a common procedure for the treatment of ISR. This randomized trial aimed to compare the efficacy of β-brachytherapy with β-radioisotopes 90 Sr/ 90 Y and paclitaxel-eluting stent implantation for the treatment of diffuse ISR. Material and methods: Thirty-seven patients with diffuse ISR were randomly assigned to β-brachytherapy after balloon angioplasty (Beta-Cath TM in 17 patients) or paclitaxel-eluting stent implantation (Taxus-Express2 TM in 20 patients). Six-month clinical follow-up was obtained for all patients, while angiographic follow-up was available for 30 patients. Results: Binary ISR (restenosis >50%) within target segment was observed in three patients treated with Beta-Cath TM , of which one needed target segment revascularisation for recurrent ISR, whereas no significant restenosis occurred in the patients treated with Taxus-Express2 TM (P = 0.037). No further major adverse cardiac (target segment revascularisation, myocardial infarction, death) was found in either group (P = NS). Stent implantation was the more time-saving (31 ± 11 min versus 60 ± 23 min, P TM arm, we found no difference in clinical outcome after implantation of paclitaxel-eluting stents for the treatment of diffuse ISR when compared to β-brachytherapy

  3. Multiscale coupling of a Lattice Boltzmann simulation of blood flow to cell- and tissue-level processes: the case of in-stent restenosis

    NARCIS (Netherlands)

    Hoekstra, A.G.; Pereira, J.C.F.; Sequeira, A.; Pereira, J.M.C.

    2010-01-01

    In-stent restenosis, the maladaptive response of a blood vessel to injury caused by the deployment of a stent, is a multiscale system involving a large number of biological and physical processes. We describe a Complex Automata Model for in-stent restenosis, coupling blood flow, drug diffusion, and

  4. Treatment of diffuse in-stent restenosis with rotational atherectomy followed by radiation therapy with a 188Re-MAG3-filled balloon: six-month clinical and angiographic results of R4 registry

    International Nuclear Information System (INIS)

    Moon, D. H.; Oh, S. J.; Park, S. W.; Hong, M. K.; Lee, C. H.; Kim, J. Z.; Park, S. J.; Lee, H. K.

    2000-01-01

    Intracoronary β-irradiation after rotational atherectomy may be a reasonable approach to prevent recurrent in-stent restenosis (ISR). This study was done to evaluate the feasibility and efficacy of β-radiation therapy with a 188 Re-MAG3-filled balloon following rotational atherectomy for ISR. Fifty consecutive patients with diffuse ISR (length >10 mm) in native coronary arteries underwent rotational atherectomy and adjunctive balloon angioplasty followed by β-irradiation using 188 Re-MAG3-filled balloon catheter. The radiation doses was 15 Gy at 1.0 mm deep into vessel wall. Mean length of the lesion and irradiated segment was 25.6±12.7 mm and 37.6±11.2 mm, respectively. The radiation was delivered successfully to all patients, with a mean irradiation time of 20.1±61 7 sec. No adverse event including myocardial infarction, death, or stent thrombosis occurred during the follow-up period (mean 10.3±3.7 mon) and non-target vessel revascularization was needed in one patient. Six-month binary angiographic restenosis rate was 10.4% (2 focal ISR and 3 edge restenosis) and loss index was 0.17±0.31. Irradiation using 188 Re-MAG3-filled balloon following rotational atherectomy for patients with diffuse ISR may improve the clinical and angiographic outcomes. Further prospective randomized trials are warranted to evaluate the synergistic effect of debulking and irradiation in patients with diffuse ISR

  5. Colchicine reduces restenosis after balloon angioplasty treatment for in-stent restenosis.

    Science.gov (United States)

    Kong, Junying; Deng, Ying; Dong, Qiang; Liu, Wenhua; Lu, Ying

    2015-02-01

    Treatment of coronary in-stent restenosis (ISR) is hampered by a high incidence of recurrent ISR. Colchicine is an old drug with known anti-inflammatory and antiproliferative actions. We evaluated the strategy of colchicine combined with conventional balloon angioplasty for the treatment of ISR. Sixty coronary arteries of 60 mini-pigs underwent oversized bare-metal stent implantation to induce ISR. After 28 days, vessels with ISR (≥50% diameter stenosis) were randomly divided into three groups: control (conventional balloon angioplasty combined with placebo), colchicine (conventional balloon angioplasty combined with colchicine) and drug-eluting balloon (DEB). Restenosis and neointima formation were elevated with angiography and histological and morphometric analysis at 28 days after different interventions. Late lumen loss and percent area stenosis at follow-up were lower in colchicine group compared to control group but were similar to those of DEB group. There was no significant difference in proliferating cell nuclear antigen-positive vascular smooth muscle cells and inflammatory score between the colchicine group and the DEB group. The efficacy of colchicine combined with conventional balloon angioplasty for treatment of ISR was comparable to that of DEB. Treatment of ISR might not require a second stent implantation, and colchicine combined with conventional balloon angioplasty seemed to be another consideration. Copyright © 2015 IMSS. Published by Elsevier Inc. All rights reserved.

  6. Quantification of in-stent restenosis parameters in rabbits by micro-CT

    International Nuclear Information System (INIS)

    Langheinrich, A.C.; Zoerb, C.; Jajima, J.; Lommel, D.; Rau, W.S.; Walker, G.; Mueller, K.M.; Bohle, R.M.

    2005-01-01

    Purpose: The well-defined model of angioplasty and stent implantation in the rabbit aorta is useful in experimental studies of restenosis. This study was performed to evaluate the feasibility of Micro-CT for quantification of in-stent restenosis in a rabbit aortic in-stent restenosis model. Material and Methods: To induce in-stent restenosis seven female New Zealand rabbits underwent balloon dilation and denudation prior to stenting the abdominal aorta. After six weeks on atherogenic diet, animals were killed and the aorta was perfused with contrast agent. Micro-CT morphometric analysis of balloon and stent injured arteries obtained by 700 transverse sections (voxel size 10 μm) was compared to conventional histological analysis. Results: Intimal hyperplasia was present in stented and balloon injured arteries with a moderate intimal area assessed by Micro-CT and conventional histology (3.91±0.5 mm 2 vs. 4.18±0.42; r=0.9). High significant correlations between Micro-CT image analysis and conventional histomorphometry were obtained for lesion size, size of media, size of lumen and stent area (r=0.84 to 0.96). Conclusion: Micro-CT is feasible for quantitative information about restenosis following balloon angioplasty and stent implantation and has the potential to become a standard technique in many laboratories which will augment serial histology as the reference method for ex-vivo studies of restenosis. (orig.)

  7. Does nickel allergy play a role in the development of in-stent restenosis?

    Science.gov (United States)

    El-Mawardy, R; Fuad, H; Abdel-Salam, Z; Ghazy, M; Nammas, W

    2011-11-01

    It was suggested that coronary in-stent restenosis might be triggered by allergy to nickel and molybdenum ions released from stainless-steel stents. We sought to explore any possible relationship between nickel allergy and in-stent restenosis. 50 patients were studied, who underwent elective follow-up coronary angiography for recurrent symptoms after prior coronary stenting, at least 3 months following the index procedure. Consecutively, we enrolled 25 patients with > or = 50% in-stent restenosis (study group), and 25 others with nickel allergy was performed using 5% nickel sulphate solution in petroleum applied as a patch test to the interscapular region by the Finn chamber method. A positive test was defined as an inflammatory response with erythema, edema, papulovesicles, or infiltration after 48 or 72 hours. The mean age of the whole study cohort was 55.9 +/- 13.9 years, 44 (88%) being males. Two patients of the study group (8%) had a history of contact allergy to metals. However, both of them showed a negative patch test result. No patient in the control group had a history of metal allergy (p > 0.05). Only one patient in the study group (4%) had a positive patch test result for nickel contact allergy, whereas all patients in the control group had a negative result (p > 0.05). Based on the available evidence, a cause-effect relationship between nickel allergy and in-stent restenosis cannot be confirmed.

  8. From histology and imaging data to models for in-stent restenosis

    NARCIS (Netherlands)

    Amatruda, C.M.; Bona Casas, C.; Keller, B.K.; Tahir, H.; Dubini, G.; Hoekstra, A.; Hose, D.R.; Lawford, P.; Migliavacca, F.; Narracott, A.J.; Gunn, J.

    2014-01-01

    The implantation of stents has been used to treat coronary artery stenosis for several decades. Although stenting is successful in restoring the vessel lumen and is a minimally invasive approach, the long-term outcomes are often compromised by in-stent restenosis (ISR). Animal models have provided

  9. Technical options for treatment of in-stent restenosis after carotid artery stenting

    NARCIS (Netherlands)

    Pourier, Vanessa E C|info:eu-repo/dai/nl/413970310; de Borst, Gert J.|info:eu-repo/dai/nl/237108151

    2016-01-01

    Objective This review summarizes the available evidence and analyzes the current trends on treatments for carotid in-stent restenosis (ISR) after carotid artery stenting (CAS). Methods An update of a 2010 review of the literature (which included 20 articles) was conducted using PubMed and Embase.

  10. Nickel and molybdenum contact allergies in patients with coronary in-stent restenosis.

    Science.gov (United States)

    Köster, R; Vieluf, D; Kiehn, M; Sommerauer, M; Kähler, J; Baldus, S; Meinertz, T; Hamm, C W

    2000-12-02

    Coronary in-stent restenosis might be triggered by contact allergy to nickel, chromate, or molybdenum ions released from stainless-steel stents. We investigated the association between allergic reactions to stent components and the occurrence of in-stent restenosis. Patients with coronary stainless-steel stents who underwent angiography for suspected restenosis were consecutively included in this study. Quantitative coronary angiography for analysis of percentage diameter stenosis was done on 131 patients (mean age 62 years [SD 9]) with 171 stents 6.1 months (2.7) after stent implantation. All patients underwent epicutaneous patch tests (Finn chamber method) for nickel, chromate, molybdenum, manganese, and small 316L stainless-steel plates. Patch tests were assessed by independent dermatologists after 48 h, 72 h, and when necessary 96 h of contact with the potential allergen. In-stent restenosis (> or =550% diameter stenosis) occurred in 89 patients. All ten patients with positive patch-test results had restenoses (p=0.03). Four male patients had positive reactions to molybdenum, and seven patients (four male, three female) had reactions to nickel. No patient with an allergic reaction to the standard test substances had a positive reaction to the stainless-steel plates. All patients with positive results had recurrent angina pectoris and needed target-vessel revascularisation. Patients with allergic patch-test reactions to nickel and molybdenum had a higher frequency of in-stent restenoses than patients without hypersensitivity. Allergic reactions to nickel and molybdenum released from stents may be one of the triggering mechanisms for in-stent restenosis.

  11. Intracoronary brachytherapy in the treatment of in-stent restenosis. Initial experience in Brazil

    Directory of Open Access Journals (Sweden)

    Fábio Sândoli de Brito Jr

    2001-09-01

    Full Text Available Intracoronary brachytherapy using beta or gamma radiation is currently the most efficient type of therapy for preventing the recurrence of coronary in-stent restenosis. Its implementation depends on the interaction among interventionists, radiotherapists, and physicists to assure the safety and quality of the method. The authors report the pioneering experience in Brazil of the treatment of 2 patients with coronary in-stent restenosis, in whom beta radiation was used as part of the international multicenter randomized PREVENT study (Proliferation REduction with Vascular ENergy Trial. The procedures were performed rapidly and did not require significant modifications in the traditional techniques used for conventional angioplasty. Alteration in the radiological protection devices of the hemodynamic laboratory were also not required, showing that intracoronary brachytherapy using beta radiation can be incorporated into the interventional tools of cardiology in our environment.

  12. Bioresorbable vascular scaffold to treat malignant in-stent restenosis in a patient with nickel allergy.

    Science.gov (United States)

    Jurado-Román, Alfonso; López-Lluva, María T; Sánchez-Pérez, Ignacio; Piqueras-Flores, Jesús; Maseda, Ramón; Lozano-Ruíz-Poveda, Fernando

    2017-09-01

    Nickel is the most frequent allergen in patients with allergic contact dermatitis and nickel allergy has been associated with recurrent in-stent restenosis. However, it is often misdiagnosed because of a low suspicion threshold. It should be discarded in patients with recurrent in-stent restenosis, especially if their medical history reveals prior contact dermatitis. It is also noteworthy and rarely specified that even newer generation stents that use novel metal alloys also contain low amounts of nickel. To avoid the implantation of new stents containing this metal, when percutaneous coronary intervention is indicated, drug eluting balloons or bioresorbable vascular scaffolds associated with small doses of steroids could provide good alternatives of treatment. To the best of our knowledge, this is the first description of this therapeutic alternative in such an exceedingly rare clinical scenario. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Relation of Nickel Allergy with in-Stent Restenosis in Patients Treated with Cobalt Chromium Stents

    OpenAIRE

    Aliağaoğlu, Cihangir; Turan, Hakan; Erden, İsmail; Albayrak, Hülya; Özhan, Hakan; Başar, Cengiz; Gürlevik, Zehra; Alçelik, Ayşegül

    2012-01-01

    Background In-stent restenosis (ISR) is the major limitation of percutaneous coronary stenting procedure. The elements like nickel, chromate and molybdenum are known to cause contact allergy. Hypersensitivity reaction, against these metal ions, may be one of the reasons of ISR. Cobalt chromium coronary stents, which are increasingly being used in percutaneous coronary interventions, have more nickel amount than the stainless steel stents. Objective We aimed to investigate the association betw...

  14. Bioabsorbable drug-eluting vascular scaffold for the treatment of coronary in-stent restenosis: A two center registry

    International Nuclear Information System (INIS)

    Moscarella, Elisabetta; Varricchio, Attilio; Stabile, Eugenio; Franzone, Anna; Granata, Francesco; Rapacciuolo, Antonio; Galasso, Gennaro; Capozzolo, Claudia; Cirillo, Plinio

    2015-01-01

    Background/purpose: Coronary in-stent restenosis (ISR) is a clinical problem for which a satisfactory solution has not been found yet. Bioabsorbable drug eluting vascular scaffolds (BVSs) provide transient vessel scaffolding combined with prolonged drug delivery capability. The aim of this study was to investigate the safety of BVS for the treatment of coronary ISR. Methods/materials: Between January 2013 and June 2013, 27 patients (31 lesions), presenting with either stable or unstable angina due to coronary ISR, were enrolled in a single arm, prospective, open label registry. Primary end point was the occurrence of target vessel revascularization (TVR) at 12 months. Secondary end point was the composite of death, myocardial infarction and TVR at 12 months. Results: A diffuse ISR pattern was present in 70% of the lesions; mean lesion length was 34.6 ± 15. BVS was successfully implanted in all patients with no in hospital MACE. At twelve months of follow up, MACE rate was 18.5%. One patient died for non-cardiac reason, one patient died due to a possible stent thrombosis and TVR was necessary in 3 patients (11.1%). Conclusions: Our data suggest that BVS is safe and technically feasible for treatment of long and diffuse coronary ISR. These data could be considered hypothesis generator for a randomized clinical trial. - Highlights: • A safe therapeutic option for the treatment of diffuse ISR; • Technically feasible; • Associated to a low rate of restenosis recurrence at nine month.

  15. Bioabsorbable drug-eluting vascular scaffold for the treatment of coronary in-stent restenosis: A two center registry

    Energy Technology Data Exchange (ETDEWEB)

    Moscarella, Elisabetta [Division of Cardiology, Seconda Università degli studi di Napoli, AO Dei cColli, PO Monaldi (Italy); Varricchio, Attilio [Division of Cardiology, Department of Advanced Biomedical Sciences, University of Napoli “Federico II”, Napoli (Italy); Stabile, Eugenio, E-mail: geko50@hotmail.com [Laboratory of Invasive Cardiology, Dipartimento di Cardiologia, Presidio Ospedaliero “Monaldi”, Azienda Ospedaliera “Dei Colli”, Napoli (Italy); Franzone, Anna [Laboratory of Invasive Cardiology, Dipartimento di Cardiologia, Presidio Ospedaliero “Monaldi”, Azienda Ospedaliera “Dei Colli”, Napoli (Italy); Granata, Francesco [Division of Cardiology, Seconda Università degli studi di Napoli, AO Dei cColli, PO Monaldi (Italy); Rapacciuolo, Antonio; Galasso, Gennaro [Laboratory of Invasive Cardiology, Dipartimento di Cardiologia, Presidio Ospedaliero “Monaldi”, Azienda Ospedaliera “Dei Colli”, Napoli (Italy); Capozzolo, Claudia [Division of Cardiology, Department of Advanced Biomedical Sciences, University of Napoli “Federico II”, Napoli (Italy); Cirillo, Plinio [Laboratory of Invasive Cardiology, Dipartimento di Cardiologia, Presidio Ospedaliero “Monaldi”, Azienda Ospedaliera “Dei Colli”, Napoli (Italy); and others

    2015-10-15

    Background/purpose: Coronary in-stent restenosis (ISR) is a clinical problem for which a satisfactory solution has not been found yet. Bioabsorbable drug eluting vascular scaffolds (BVSs) provide transient vessel scaffolding combined with prolonged drug delivery capability. The aim of this study was to investigate the safety of BVS for the treatment of coronary ISR. Methods/materials: Between January 2013 and June 2013, 27 patients (31 lesions), presenting with either stable or unstable angina due to coronary ISR, were enrolled in a single arm, prospective, open label registry. Primary end point was the occurrence of target vessel revascularization (TVR) at 12 months. Secondary end point was the composite of death, myocardial infarction and TVR at 12 months. Results: A diffuse ISR pattern was present in 70% of the lesions; mean lesion length was 34.6 ± 15. BVS was successfully implanted in all patients with no in hospital MACE. At twelve months of follow up, MACE rate was 18.5%. One patient died for non-cardiac reason, one patient died due to a possible stent thrombosis and TVR was necessary in 3 patients (11.1%). Conclusions: Our data suggest that BVS is safe and technically feasible for treatment of long and diffuse coronary ISR. These data could be considered hypothesis generator for a randomized clinical trial. - Highlights: • A safe therapeutic option for the treatment of diffuse ISR; • Technically feasible; • Associated to a low rate of restenosis recurrence at nine month.

  16. In-stent restenosis of innominate artery with critical stenosis of right internal carotid artery

    International Nuclear Information System (INIS)

    Hussain, S.; Raza, A.; Ahmed, W.

    2011-01-01

    A lady with aortitis syndrome developed in-stent restenosis (ISR) of the innominate artery stent and critical stenosis of right internal carotid artery. The therapeutic challenge was gaining access to the carotid vessel, after treating the innominate artery ISR and all the while using distal protection to circumvent potential cerebral embolism. Percutaneous transluminal angioplasty (PTA) with or without stenting is a safe therapeutic option for re-vascularization of the supra aortic vessels. In the event of re-stenosis, re-treatment with PTA and stenting is safe. Ample evidence-base exists now for carotid artery stenting (CAS) in preference to carotid endarterectomy in patients with stenotic lesions of the carotid vessels. (author)

  17. Safety and efficacy of everolimus-eluting stents for bare-metal in-stent restenosis

    International Nuclear Information System (INIS)

    Ota, Hideaki; Mahmoudi, Michael; Torguson, Rebecca; Satler, Lowell F.; Suddath, William O.; Pichard, Augusto D.; Waksman, Ron

    2015-01-01

    Objective: The aim of this study was to compare the safety and efficacy of the everolimus-eluting stents (EES) with the paclitaxel-eluting stent (PES) and sirolimus-eluting stent (SES) for the treatment of bare-metal in-stent restenosis. Background: The optimal treatment for bare-metal in-stent restenosis remains controversial. Methods: The study cohort comprised 322 consecutive patients (543 lesions) who presented with bare-metal in-stent restenosis to our institution and underwent coronary artery stent implantation with EES (114 patients; 181 lesions), PES (65 patients; 116 lesions) and SES (143 patients; 246 lesions). The analyzed clinical parameters were the 1-year rates of death, Q-wave myocardial infarction (MI), target lesion revascularization (TLR), target vessel revascularization (TVR), definite stent thrombosis (ST) and major adverse cardiac events (MACE) defined as the composite of death, MI, or TLR at 1-year. Results: The three groups were well matched for the conventional risk factors except for age and chronic kidney disease. The 1-year analyzed clinical parameters were similar in the three groups: death (EES = 3.5%, PES = 4.6%, SES = 4.2%; p = 0.94), MI (EES = 3.5%, PES = 6.3%, SES = 2.1%; p = 0.31), TLR (EES = 9.8%, PES = 9.5%, SES = 5.7%; p = 0.42), TVR (EES = 14.3%, PES = 11.1%, SES = 11.3%; p = 0.74), definite ST (EES = 0.9%, PES = 3.1%, SES = 3.5%; p = 0.38) and MACE (EES = 14.0%, PES = 15.4%, SES = 10.5%; p = 0.54). Male gender (hazard ratio = 0.47; 95% confidence interval = 0.25–0.88) and number of treated lesions (hazard ratio = 1.47; 95% confidence interval = 1.06–2.05) were found to be independent predictors of MACE. Conclusion: The results of the present study indicate that EES may provide similar safety and efficacy as first generation DES for the treatment of patients presenting with bare-metal in-stent restenosis

  18. Safety and efficacy of everolimus-eluting stents for bare-metal in-stent restenosis

    Energy Technology Data Exchange (ETDEWEB)

    Ota, Hideaki [Division of Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC 20010 (United States); Mahmoudi, Michael [University of Surrey, Guildford Road, Surrey, GU2-7XH (United Kingdom); Torguson, Rebecca; Satler, Lowell F.; Suddath, William O.; Pichard, Augusto D. [Division of Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC 20010 (United States); Waksman, Ron, E-mail: ron.waksman@medstar.net [Division of Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC 20010 (United States)

    2015-04-15

    Objective: The aim of this study was to compare the safety and efficacy of the everolimus-eluting stents (EES) with the paclitaxel-eluting stent (PES) and sirolimus-eluting stent (SES) for the treatment of bare-metal in-stent restenosis. Background: The optimal treatment for bare-metal in-stent restenosis remains controversial. Methods: The study cohort comprised 322 consecutive patients (543 lesions) who presented with bare-metal in-stent restenosis to our institution and underwent coronary artery stent implantation with EES (114 patients; 181 lesions), PES (65 patients; 116 lesions) and SES (143 patients; 246 lesions). The analyzed clinical parameters were the 1-year rates of death, Q-wave myocardial infarction (MI), target lesion revascularization (TLR), target vessel revascularization (TVR), definite stent thrombosis (ST) and major adverse cardiac events (MACE) defined as the composite of death, MI, or TLR at 1-year. Results: The three groups were well matched for the conventional risk factors except for age and chronic kidney disease. The 1-year analyzed clinical parameters were similar in the three groups: death (EES = 3.5%, PES = 4.6%, SES = 4.2%; p = 0.94), MI (EES = 3.5%, PES = 6.3%, SES = 2.1%; p = 0.31), TLR (EES = 9.8%, PES = 9.5%, SES = 5.7%; p = 0.42), TVR (EES = 14.3%, PES = 11.1%, SES = 11.3%; p = 0.74), definite ST (EES = 0.9%, PES = 3.1%, SES = 3.5%; p = 0.38) and MACE (EES = 14.0%, PES = 15.4%, SES = 10.5%; p = 0.54). Male gender (hazard ratio = 0.47; 95% confidence interval = 0.25–0.88) and number of treated lesions (hazard ratio = 1.47; 95% confidence interval = 1.06–2.05) were found to be independent predictors of MACE. Conclusion: The results of the present study indicate that EES may provide similar safety and efficacy as first generation DES for the treatment of patients presenting with bare-metal in-stent restenosis.

  19. Incidence of definite stent thrombosis or in-stent restenosis after drug-eluting stent implantation for treatment of coronary in-stent restenosis. From western denmark heart registry

    DEFF Research Database (Denmark)

    Jensen, Jesper; Jensen, Lisette Okkels; Terkelsen, Christian Juhl

    2012-01-01

    There are limited data on the optimal management of in-stent restenosis after percutaneous coronary intervention (PCI) with bare metal stent (BMS) or drug-eluting stent (DES) implantations. We assessed the clinical presentation, the incidence, and prognosis of definite stent thrombosis or resteno......There are limited data on the optimal management of in-stent restenosis after percutaneous coronary intervention (PCI) with bare metal stent (BMS) or drug-eluting stent (DES) implantations. We assessed the clinical presentation, the incidence, and prognosis of definite stent thrombosis...

  20. Simple balloon dilation for drug-eluting in-stent restenosis: An optical coherent tomography analysis

    Energy Technology Data Exchange (ETDEWEB)

    Arikawa, Ryo [Division of Cardiology, Tenyoukai Central Hospital, Izumi-cho, Kagoshima City, Kagoshima (Japan); Yamaguchi, Hiroshi, E-mail: hyamaguchi@tsm.bbiq.jp [Division of Cardiology, Tenyoukai Central Hospital, Izumi-cho, Kagoshima City, Kagoshima (Japan); Takaoka, Junichiro; Miyamura, Akihiro; Atsuchi, Nobuhiko; Ninomiya, Toshiko; Atsuchi, Yoshihiko [Division of Cardiology, Tenyoukai Central Hospital, Izumi-cho, Kagoshima City, Kagoshima (Japan); Ohishi, Mitsuru [Department of Cardiovascular Medicine and Hypertension, Graduate School of Medical and Dental Science, Kagoshima University, Kagoshima (Japan); Terashima, Mitsuyasu [Department of Cardiology, Toyohashi Heart Center, Toyohashi (Japan); Kaneda, Hideaki [Okinaka Memorial Institute for Medical Research, Tokyo (Japan)

    2015-01-15

    Background: Although drug-eluting stent (DES) has significantly reduced restenosis, the treatment of DES-in-stent restenosis (ISR) remains a challenge with high restenosis rate. Methods: We examined whether morphologic appearance of restenosis tissue by optical coherent tomography (OCT) had an impact on outcomes after balloon angioplasty for DES-ISR. The morphologic appearance of restenosis tissue was qualitatively assessed for tissue structures such as homogeneous, layered, and heterogeneous patterns. Results: Using OCT, 50 patients with DES-ISR were divided into 2 groups: 25 lesions with homogeneous or layered patterns (homo/layered group) and 25 lesions with heterogeneous patterns (hetero group). Acute gain was larger in the hetero group (1.33 ± 0.41 mm vs. 1.06 ± 0.32 mm in the homo/layered group, P = 0.03). On intravascular ultrasound analysis, post-procedural percent neointimal area was smaller in the hetero group (27.4 ± 9.2% vs. 34.0 ± 11.2% in the homo/layered group, P = 0.05). Angiographic follow-up was performed in 37 lesions (74%). Follow-up minimal lumen diameter was larger in the hetero group (1.75 ± 0.89 mm vs. 1.01 ± 0.81 mm in the homo/layered group, P = 0.04). Target lesion revascularization rates tended to be lower in the hetero group (20% vs. 43% in the homo/layered group, P = 0.12). Conclusions: Balloon angioplasty was more effective for DES-ISR with heterogeneous tissue appearance than DES-ISR with homogeneous/layered tissue appearance. OCT assessment of DES-ISR morphology may be a useful adjunct in determining clinical strategies. Simple balloon dilatation is a possible treatment strategy for DES-ISR lesions with a heterogeneous appearance on OCT images.

  1. Late In-Stent Restenosis of the Abdominal Aorta in a Patient with Takayasu's Arteritis and Related Pathology

    International Nuclear Information System (INIS)

    Ishibashi-Ueda, Hatsue; Yutani, Chikao; Kuribayashi, Sachio; Takamiya, Makoto; Imakita, Masami; Ando, Motomi

    1999-01-01

    This report describes an in-stent restenosis of the infrarenal aorta in a patient with Takayasu's arteritis in a nonactive state. A 10-mm-diameter Wallstent had been deployed 42 months previously. The stented restenosed segment was replaced by a surgical graft. Histopathological examination of the excised aortic segment showed a thin layer of fibrocellular neointima and massive organized and calcified thrombus. To our knowledge, this is the first histopathological report of a late in-stent restenosis of the abdominal aorta in Takayasu's arteritis. RID='''' ID='''' Correspondence to: H. Ishibashi-Ueda, M.D

  2. The role of drug-coated balloons in in-stent restenosis.

    Science.gov (United States)

    Andrassy, Martin; Celik, Sultan; Andrassy, Joachim; Lichtenberg, Michael K; Brodmann, Marianne

    2017-08-01

    Despite a constantly expanding spectrum of therapeutic options for lower limb artery disease, there is not yet a well-defined consensus on the specific type of endovascular treatment that is best suited. Clinical data on patients with femoropopliteal disease treated with drug-coated balloons have not been elaborated sufficiently, especially in the case of in-stent restenosis. For this review a systematic research of the medical databases (Pubmed) has been conducted. Keywords such as "drug-coated balloons" (DCB), "drug-eluting balloons," "in-stent restenosis", "de novo stenosis", "angioplasty", "superficial femoral artery," "popliteal artery," "above the knee," "below the knee," "peripheral artery disease" (PAD) have been used. Furthermore, data from reviews, original contributions regarding randomized controlled studies, observational studies, registries and single center experiences have been included. Many trials have shown superiority for DCB- over percutaneous transluminal angioplasty-treatment alone in TASC IIA and TASC IIB femoropopliteal lesions. However, the currently available DCB systems are different in terms of efficacy and long-term outcomes depending on their mechanical and pharmacological features. Moreover, angiographic characteristics of femoropopliteal lesions classified by Tosaka seem to influence subsequent outcomes of DCB treatment. Lastly, there is still lack of reliable prospective long-term data regarding DCB technology.

  3. Diagnostic accuracy of 64-slice multidetector CT for detection of in-stent restenosis in an unselected, consecutive patient population

    Energy Technology Data Exchange (ETDEWEB)

    Haraldsdottir, Sigurdis, E-mail: sigurdisha@gmail.com [Boston Medical Center, 72 East Concord Street (Evans 124), Boston, MA, 02118 (United States); Gudnason, Thorarinn, E-mail: thorgudn@landspitali.is [Landspitali University Hospital, Hringbraut, 101 Reykjavik (Iceland); Sigurdsson, Axel F., E-mail: axelfsig@landspitali.is [Landspitali University Hospital, Hringbraut, 101 Reykjavik (Iceland); Gudjonsdottir, Jonina, E-mail: jonina@rd.is [Rontgen Domus Medica, Egilsgata 3, 101 Reykjavik (Iceland); Lehman, Sam J., E-mail: slehman@partners.org [Massachusetts General Hospital, 165 Cambridge Street, Suite 400, Boston, MA 02114 (United States); Eyjolfsson, Kristjan, E-mail: kristey@landspitali.is [Landspitali University Hospital, Hringbraut, 101 Reykjavik (Iceland); Scheving, Sigurpall S., E-mail: sigurpal@landspitali.is [Landspitali University Hospital, Hringbraut, 101 Reykjavik (Iceland); Gibson, C. Michael, E-mail: mgibson@perfuse.org [Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02115 (United States); Hoffmann, Udo, E-mail: uhoffmann@partners.org [Massachusetts General Hospital, 165 Cambridge Street, Suite 400, Boston, MA 02114 (United States); Jonsdottir, Birna, E-mail: birna@rd.is [Rontgen Domus Medica, Egilsgata 3, 101 Reykjavik (Iceland); Andersen, Karl, E-mail: andersen@landspitali.is [Landspitali University Hospital, Hringbraut, 101 Reykjavik (Iceland)

    2010-11-15

    Objectives: To investigate the diagnostic accuracy of 64-slice multidetector computed tomography (64-CT) for detection of in-stent restenosis (ISR) in an unselected, consecutive patient population. Background: Detection of in-stent restenosis by cardiac CT would be a major advance for the evaluation of patients suspected of having ISR. However, the diagnostic accuracy of current generation 64-CT in this context is not fully established. Methods: We conducted a prospective study on patients with stable angina or acute coronary syndrome with no prior history of coronary artery disease. Six months after percutaneous coronary intervention (PCI) with stent placement they underwent a 64-CT scan (Toshiba Multi-Slice Aquilion 64) and consequently a repeat coronary angiography for comparison. Cardiac CT data sets were analyzed for the presence of in-stent restenosis by two independent expert readers blinded to the coronary angiographic data. Results: Ninety-three patients with a total of 140 stents were evaluated. Males comprised 82% of the study group and the mean age was 63 {+-} 10 years. The mean time from PCI to the repeat coronary angiography was 208 {+-} 37 days and the mean time from 64-CT to repeat coronary angiography was 3.7 {+-} 4.9 days. The restenosis rate according to coronary angiography was 26%. Stent diameter, strut thickness, heart rate and body mass index (BMI) significantly affected image quality. The sensitivity, specificity, positive and negative predictive values of 64-CT for detection of in-stent restenosis were 27%, 95%, 67% and 78%, respectively. Conclusions: Current generation, 64-slice CT, remains limited in its ability to accurately detect in-stent restenosis.

  4. The SABRE Trial (Sirolimus Angioplasty Balloon for Coronary In-Stent Restenosis) : Angiographic Results and 1-Year Clinical Outcomes

    NARCIS (Netherlands)

    Verheye, Stefan; Vrolix, Mathias; Kumsars, Indulis; Erglis, Andrejs; Sondore, Dace; Agostoni, Pierfrancesco|info:eu-repo/dai/nl/34169276X; Cornelis, Kristoff; Janssens, Luc P F; Maeng, Michael; Slagboom, Ton; Amoroso, Giovanni; Jensen, Lisette Okkels; Granada, Juan F; Stella, Pieter|info:eu-repo/dai/nl/304814717

    2017-01-01

    Objectives The aim of this first-in-human study was to assess the safety and effectiveness of the Virtue sirolimus-eluting balloon in a cohort of patients with in-stent restenosis (ISR). Background Angioplasty balloons coated with the cytotoxic drug paclitaxel have been widely used for ISR

  5. A Comparison of Fully-Coupled 3D In-Stent Restenosis Simulations to In-vivo Data

    NARCIS (Netherlands)

    Zun, P.S.; Anikina, T.; Svitenkov, A.I.; Hoekstra, A.G.

    We describe our fully-coupled 3D multiscale model of in-stent restenosis, with blood flow simulations coupled to smooth muscle cell proliferation, and report results of numerical simulations performed with this model. This novel model is based on several previously reported 2D models. We study the

  6. The risk and prognostic impact of definite stent thrombosis or in-stent restenosis after coronary stent implantation

    DEFF Research Database (Denmark)

    Thayssen, Per; Jensen, Lisette Okkels; Lassen, Jens Flensted

    2012-01-01

    as time-dependent variables. A total of 12,277 patients were treated with stent implantation. Stent thrombosis was observed in 111 (0.9%) patients and in-stent restenosis in 503 (4.1%) patients within 12 months after the index PCI. Occurrence of stent thrombosis was associated with an increased risk...

  7. Clinical results of Intracoronary Brachytherapy (ICBT) for multiple in-stent restenosis

    Energy Technology Data Exchange (ETDEWEB)

    Stadler, P. [Dept. of Radiotherapy and Radiation Oncology, Univ. Hospital Regensburg (Germany); Praxis Muehleninsel, Landshut-Muehldorf-Dingolfing (Germany); Schaefer, C.; Chaber, S.; Putnik, K.; Treutwein, M.; Koelbl, O. [Dept. of Radiotherapy and Radiation Oncology, Univ. Hospital Regensburg (Germany); Muders, F. [Dept. of Cardiology, Univ. Hospital Regensburg (Germany)

    2006-06-15

    Background and purpose: treatment of in-stent restenosis (ISR) with percutaneous coronary intervention (PCI) alone is often followed by early re-restenosis. The present study focused on the effect of intracoronary brachytherapy (ICBT) on multiple in-stent restenosis (MISR) after repeated PCI. Patients and methods: 40 patients (27 male, 13 female, age: 66 {+-} 9 years) with MISR (two to six ISRs, median three ISRs) were retrospectively analyzed. All patients were treated by using the Novoste {sup registered} Beta-Cath trademark 3.5F System after PCI. The target vessel received 18.4-25.3 Gy of radiation at a depth of 2 mm from the center of the source. The restenosis-free survival and overall survival were calculated by Kaplan-Meier analysis (log-rank). The time interval between last PCI without ICBT and the consecutive recurrence was compared with the follow-up time after PCI with ICBT. Results: the 3-year overall survival rate after ICBT was 93%. The 0.5-, 1-, 2-, and 3-year ISR-free survival rates after PCI + ICBT were 81%, 72%, 52%, and 38%, respectively. After PCI alone, the 0.5-, 1-, and 2-year ISR-free survival rates were 30%, 13%, and 0%, respectively. This difference was highly significant (p < 0.0001). Patients with more than three ISRs before ICBT had a better outcome (3-year ISR-free survival: 80%) than patients with only two or three ISRs before ICBT (3-year ISR-free survival: 25%; p < 0.05). Conclusion: ICBT is highly effective and safe in patients with ISR. The results of this study are in accordance with the WRIST and BETA-WRIST data. After 6 months both studies revealed an ISR-free survival rate of 86% (WRIST) and 66% (BETA-WRIST), respectively. The ISR rates in the own control group (70%) were comparable to the placebo groups in WRIST (68%) and BETA-WRIST (72%). Interestingly, patients with more than three ISRs before ICBT had the lowest ISR rate after ICBT. (orig.)

  8. Clinical results of Intracoronary Brachytherapy (ICBT) for multiple in-stent restenosis

    International Nuclear Information System (INIS)

    Stadler, P.; Schaefer, C.; Chaber, S.; Putnik, K.; Treutwein, M.; Koelbl, O.; Muders, F.

    2006-01-01

    Background and purpose: treatment of in-stent restenosis (ISR) with percutaneous coronary intervention (PCI) alone is often followed by early re-restenosis. The present study focused on the effect of intracoronary brachytherapy (ICBT) on multiple in-stent restenosis (MISR) after repeated PCI. Patients and methods: 40 patients (27 male, 13 female, age: 66 ± 9 years) with MISR (two to six ISRs, median three ISRs) were retrospectively analyzed. All patients were treated by using the Novoste registered Beta-Cath trademark 3.5F System after PCI. The target vessel received 18.4-25.3 Gy of radiation at a depth of 2 mm from the center of the source. The restenosis-free survival and overall survival were calculated by Kaplan-Meier analysis (log-rank). The time interval between last PCI without ICBT and the consecutive recurrence was compared with the follow-up time after PCI with ICBT. Results: the 3-year overall survival rate after ICBT was 93%. The 0.5-, 1-, 2-, and 3-year ISR-free survival rates after PCI + ICBT were 81%, 72%, 52%, and 38%, respectively. After PCI alone, the 0.5-, 1-, and 2-year ISR-free survival rates were 30%, 13%, and 0%, respectively. This difference was highly significant (p < 0.0001). Patients with more than three ISRs before ICBT had a better outcome (3-year ISR-free survival: 80%) than patients with only two or three ISRs before ICBT (3-year ISR-free survival: 25%; p < 0.05). Conclusion: ICBT is highly effective and safe in patients with ISR. The results of this study are in accordance with the WRIST and BETA-WRIST data. After 6 months both studies revealed an ISR-free survival rate of 86% (WRIST) and 66% (BETA-WRIST), respectively. The ISR rates in the own control group (70%) were comparable to the placebo groups in WRIST (68%) and BETA-WRIST (72%). Interestingly, patients with more than three ISRs before ICBT had the lowest ISR rate after ICBT. (orig.)

  9. Bioresorbable vascular scaffold for coronary in-stent restenosis: A novel concept

    Directory of Open Access Journals (Sweden)

    Surender Deora

    2014-07-01

    Full Text Available The management of patients with significant in-stent restenosis (ISR with drug-eluting stent is still not well defined. Various treatment modalities include plain old balloon angioplasty (POBA, metallic stent, cutting or scoring balloon and drug-eluting balloon (DEB. Bioresorbable vascular scaffold (BVS is the latest technology for the treatment of de novo coronary artery lesions. The use of BVS in ISR is based on the rationale of local drug delivery as achieved by DEB without the permanent bi-layer of metal and also stabilizes dissection flaps and prevents acute recoil as provided by metallic stent. To the best of our knowledge this is the first case report of the use of BVS in patient with ISR.

  10. Novel Use of an Orbital Atherectomy Device for In-Stent Restenosis: Lessons Learned

    Directory of Open Access Journals (Sweden)

    K. Shaikh

    2016-01-01

    Full Text Available We present a case of a 67-year-old man with stage III chronic kidney disease, uncontrolled diabetes mellitus, coronary artery disease, and high surgical risk who presented with two episodes of acute coronary syndrome attributed to in-stent restenosis (ISR associated with heavily calcified lesions. In this case, we were able to improve luminal patency with orbital atherectomy system (OAS; however, withdrawal of the device resulted in a device/stent interaction, causing failure of the device. Given limitations in current evidence and therapies, managing ISR can be a technical and cognitive challenge. Balloon expansion of the affected region often provides unsatisfactory results, possibly related to significant calcium burden. OAS could be an efficacious way of reestablishing luminal patency in ISR lesions, as these lesions are often heavily calcified.

  11. Factors Associated with In-stent Restenosis in Patients Following Percutaneous Coronary Intervention

    Directory of Open Access Journals (Sweden)

    Dedi Wihanda

    2015-07-01

    Full Text Available Aim: to determine factors associated with In-Stent Restenosis (ISR in patients following Percutaneous Coronary Intervention (PCI. Methods: a retrospective cross-sectional study was conducted using secondary information from medical records of post-PCI patients who underwent follow-up of angiography PCI between January 2009 and March 2014 at The Integrated Cardiovascular Service Unit, Cipto Mangunkusumo Hospital, Jakarta. Angiographic ISR was defined when the diameter of stenosis ≥50% at follow-up angiography including the diameter inside the stent and diameter with five-mm protrusion out of the proximal and distal ends of the stent. Results: there were 289 subjects including 133 subjects with and 156 subjects without ISR. The incidence of ISR in patients using of bare-metal stent (BMS and drug-eluting stent (DES were 61.3% and 40.7%, respectively. Factors associated with ISR are stent-type (OR=4.83, 95% CI 2.51-9.30, stent length (OR=3.71, 95% CI 1.99-6.90, bifurcation lesions (OR=2.43, 95% CI 1.16-5.10, smoking (OR=2.30, 95% CI 1.33-3.99, vascular diameter (OR=2.18, 95% CI 1.2-3.73, hypertension (OR=2.16, 95% CI 1.16-4.04 and diabetes mellitus (OR=2.14, 95% CI 1.23-3.70. Conclusion: stent type, stent length, bifurcation lesions, smoking, vascular diameter, hypertension and DM are factors associated with ISR in patients following PCI. Key words: bare-metal stent; drug-eluting stent; in-stent restenosis.

  12. No association between metal allergy and cardiac in-stent restenosis in patients with dermatitis-results from a linkage study

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Engkilde, Kåre; Menné, Torkil

    2011-01-01

    , and it remains unclear whether individuals who are allergic to these metals have an increased risk of restenosis after PCI with stent implantation. Objectives. To further evaluate whether dermatitis patients with nickel and/or chromium allergy had an increased risk of developing cardiac in-stent restenosis...... restenosis. Conclusions. Nickel and/or chromium allergy in dermatitis patients does not appear to increase the overall risk of in-stent restenosis after PCI.......Background. Percutaneous coronary intervention (PCI) with implantation of a metal stent is a common procedure performed in patients with symptomatic ischaemic heart disease. Intracoronary stents typically have a backbone of stainless steel, which contains nickel, chromium, and molybdenum...

  13. Relation of Nickel Allergy with in-Stent Restenosis in Patients Treated with Cobalt Chromium Stents.

    Science.gov (United States)

    Aliağaoğlu, Cihangir; Turan, Hakan; Erden, Ismail; Albayrak, Hülya; Ozhan, Hakan; Başar, Cengiz; Gürlevik, Zehra; Alçelik, Ayşegül

    2012-11-01

    In-stent restenosis (ISR) is the major limitation of percutaneous coronary stenting procedure. The elements like nickel, chromate and molybdenum are known to cause contact allergy. Hypersensitivity reaction, against these metal ions, may be one of the reasons of ISR. Cobalt chromium coronary stents, which are increasingly being used in percutaneous coronary interventions, have more nickel amount than the stainless steel stents. We aimed to investigate the association between nickel hypersensitivity reaction and ISR in patients treated with cobalt chromium coronary stents. Epicutaneous patch tests for nickel were applied to 31 patients who had undergone elective cobalt chromium coronary stent implantation and had ISR in control angiogram. Thirty patients, without ISR, were included as the control group. Patch test results and other clinical variables were compared. There was no statistically significant difference of the mean age, sex, body mass index, rate of hypercholesterolemia, diabetes, hypertension and smoking between the patients with and without ISR. All other lesion characteristics were similar in the 2 groups. According to the patch test results, 7 patients had nickel contact allergy. All of these patients were in the ISR group, which was statistically significant (pnickel allergy than the control group. Nickel allergy may play role in restenosis pathophysiology.

  14. Clinical evaluation and stress test have limited value in the diagnosis of in-stent restenosis.

    Science.gov (United States)

    Andersen, Karl; Steinthórsdóttir, Sandra Dís; Haraldsdottir, Sigurdis; Gudnason, Thorarinn

    2009-12-01

    In-stent restenosis (ISR) is the main limitation of percutaneous coronary interventions (PCI), occurring in approximately 25% of cases. Although frequently asymptomatic, many PCI patients present with recurrent symptoms of chest pain at follow-up raising a clinical suspicion of ISR. The diagnosis of ISR can be challenging in these patients and difficult to rule out without repeat coronary angiography. We prospectively investigated the diagnostic accuracy of clinical evaluation and exercise stress testing to detect ISR as compared to coronary angiography, in a consecutive, unselected cohort of PCI patients. We studied 91 patients with a total of 143 stents. Clinical evaluation predicted ISR to be likely in 19% of cases and the exercise test was positive in 29%. The binary restenosis rate was 21%. Clinical evaluation had a positive predictive value of 29% and accuracy of 71%, while exercise stress testing had a positive predictive value of 19% and accuracy of 65%. In conclusion, we found the diagnostic accuracy of clinical evaluation to be low and not significantly improved by exercise stress testing when evaluating PCI patients for ISR.

  15. The initial course of in-stent restenosis influences the response to vascular brachytherapy

    International Nuclear Information System (INIS)

    Cheneau, Edouard; Leborgne, Laurent; Wolfram, Roswitha; Dilcher, Christian; Pakala, Rajbabu; Pichard, Augusto D.; Satler, Lowell F.; Canos, Daniel; Lindsay, Joseph; Waksman, Ron

    2002-01-01

    Background: Vascular brachytherapy (VBT) reduces the rate of recurrence of in-stent restenosis (ISR) by inhibiting intimal proliferation. However, the rate of cell proliferation, reflected by the speed of ISR development, is variable in ISR lesions and might influence the responsiveness of ISR to radiation. The aim of this study was to determine the influence of the initial ISR course on the clinical outcome of patients undergoing VBT. Methods: In 1165 patients treated for ISR with VBT in the WRIST studies, we determined the time for ISR (time between initial stent implantation and restenosis), the time for VBT treatment (time between stent implantation and VBT), and previous ISR treatment with conventional strategies. Target lesion revascularization (TLR) at 6 months was available in all patients. Results: Previous ISR treatment did not influence the result of VBT (TLR was 17% vs. 16% without previous angioplasty). Time to ISR influences the outcome of patients undergoing VBT; TLR decreased when ISR occurred later. TLR was 18.2%, 16.7%, and 11.1% when time to ISR was 270 days, respectively, P=.03. Early ISR (time for ISR <90 days) is a factor for radiation failure (OR=2.1, P<.05). In patients with early ISR, TLR is lower when VBT is delayed; TLR was 11% if performed 90 days after stent implantation as compared to 22% if VBT is performed early (<90 days), P<.05. Conclusion: The course of ISR development affects the long-term efficacy of VBT. Early restenosis remains a factor of treatment failure in the VBT era. Delaying VBT beyond 90 days after stent implantation reduces the rate of subsequent revascularization in these patients

  16. Which is currently the best strategy for treatment of SFA in-stent restenosis?

    Science.gov (United States)

    Elens, M; Verbist, J; Keirse, K; Van Den Eynde, W; Peeters, P

    2014-08-01

    Stents have been created to prevent vessel recoil after percutaneous transluminal angioplasty (PTA). Despite the evolution in stent design, intimal hyperplasia and stent fractures and the resulting in-stent restenosis (ISR) still occur. Different strategies to treat ISR have been described with variable results in patency rates in the short and the long-term. PTA only in the treatment of ISR showed high procedural success, but the mid and long-term patency rates were very disappointing. Atherectomy devices have showed same insufficient results. If stent fracture is the cause of the ISR, the fracture has to be overstent. The best two options are covered stents and drug eluting stents (DES). Drug eluting devices like DES and drug eluting balloons (DEBs) showed promising results, with patency rates up to over 90% after one year. DEBs have the advantage of leaving nothing behind. Combined treatment of ISR with atherectomy and DEB has a similar good result. Endovascular brachytherapy showed high patency rates after one year but this technique is limited due to the time-consuming nature of the procedure, complex radiation safety measurements, and staffing requirements. Overall drug-eluting devices are emerging as the best treatment of SFA ISR with patency rates over 90% after 2 years.

  17. Angiographic patterns of in-stent restenosis classified by computed tomography in patients with drug-eluting stents: correlation with invasive coronary angiography

    International Nuclear Information System (INIS)

    Pan, Jingwei; Lu, Zhigang; Wei, Meng; Zhang, Jiayin; Li, Minghua

    2013-01-01

    To evaluate the diagnostic accuracy of Mehran's in-stent restenosis (ISR) classification by coronary computed angiography (CCTA), with reference to invasive coronary angiography (ICA). Consecutive symptomatic patients, who had clinically suspected ISR and implanted stent diameter ≥ 3 mm, were prospectively enrolled in our study. Mehran's classification was employed by CCTA and ICA to classify ISR lesions into four subtypes: focal, diffuse intrastent, diffuse proliferative and total occlusion. CCTA and ICA measurement of lesion length was further compared. Sixty-one patients with 101 implanted stents were included in our study. The overall sensitivity, specificity, PPV and NPV of CCTA diagnosis of binary ISR, as shown by patient-based analysis (n = 61), were 100 % (49/49), 75 % (8/12), 92.45 % (49/53) and 100 % (8/8) respectively. Mehran's classification of CCTA correlated well with ICA findings. The diagnostic accuracy of CCTA for class I, class II, class III and class IV lesions was 92.5 %, 91.67 %, 100 % and 100 % respectively. Lesion length was assessed to be significantly longer with CCTA than with ICA (11.03 ± 5.89 mm versus 8.56 ± 4.99 mm, P < 0.001). Angiographic patterns of in-stent restenosis can be accurately classified by coronary computed angiography. The lesion length measured by CCTA is longer than that assessed by invasive coronary angiography. (orig.)

  18. CYP2C19⁎2 Polymorphism in Chilean Patients with In-Stent Restenosis Development and Controls

    Directory of Open Access Journals (Sweden)

    Jenny Ruedlinger

    2017-01-01

    Full Text Available Clopidogrel is an antiplatelet drug especially used in patients undergoing percutaneous coronary interventions (PCI. Polymorphisms within CYP2C19 can result in important interindividual variations regarding therapeutic efficacy. Therefore, we aimed to evaluate the impact of the CYP2C19⁎2 variant (rs4244285 on in-stent restenosis occurrence in Chilean patients who underwent PCI and received clopidogrel. A total of 77 cases with stenosis >50% in the angioplasty site (62.75 ± 9.8 years, 80.5% males and 86 controls (65.45 ± 9.8 years, 72.1% males were studied. The polymorphism was genotyped using TaqMan® Drug Metabolism Genotyping Assays. Overall, CYP2C19⁎2 allele frequency was 8.3%. Diabetes, chronic lesions, and bare metal stents (BMS were observed more often in cases than in controls (p = 0.05, p = 0.04, and p = 0.02, resp.. Genotypic frequencies did not differ significantly between the groups (p = 0.15. Nonetheless, the mutated allele was observed in a greater proportion in patients without in-stent restenosis (p = 0.055. There was no significant association between the rs4244285 variant and the occurrence of in-stent restenosis after PCI (OR = 0.44; 95% CI: 0.19 to 1.04; p = 0.06. In summary, no association was identified between the CYP2C19⁎2 variant and the development of coronary in-stent restenosis.

  19. Diagnostic accuracy of coronary in-stent restenosis using 320-row multidetector computed tomography

    International Nuclear Information System (INIS)

    Koeda, Tatsuhiko; Fusazaki, Tetsuya; Niinuma, Hiroyuki; Itoh, Tomonori; Tanaka, Ryoichi; Yoshioka, Kunihiro; Nakamura, Motoyuki

    2010-01-01

    Although a multidetector computed tomography (MDCT) was useful in assessing coronary artery disease, there were several limitations in detecting coronary in-stent restenosis (ISR). The aim of this study was to evaluate the diagnostic accuracy of coronary ISR using a 320-row MDCT (area detector computed tomography: ADCT) in patients after stent implantation. We performed ADCT in consecutive 102 patients (133 lesions) before coronary arteriography (CAG). In 133 lesions, 74 were treated with bare metal stents and 59 with drug eluting stents. The diagnostic accuracy of ADCT for coronary ISR was compared to the results of CAG. ISR was found in 18 cases with CAG analysis. To compare with CAG, sensitivity, specificity, positive predictive value, and negative predictive value to evaluate ISR by ADCT were 100%, 87.8%, 56.3% and 100% respectively. The ISR in a wide range of coronary artery disease was detected by ADCT with good diagnostic accuracy. ADCT may be a promising noninvasive diagnostic imaging modality to evaluate coronary ISR. (author)

  20. The value of matrix metalloproteinase in predicting the in-stent restenosis after percutaneous coronary intervention procedure

    International Nuclear Information System (INIS)

    Xu Zhaoyan; Yang Xili

    2011-01-01

    Objective: To discuss the relationship between the concentration of matrix metalloproteinase (MMP-1, MMP-9) and the in-stent restenosis after percutaneous coronary intervention procedure (PCI). Methods: During the period from June 2006 to June 2008, PCI procedure was carried out in 206 patients with coronary artery disease in authors' hospital. After the procedure, both coronary angiography and intravascular ultrasonography (IVUS) were conducted during follow-up period. Base on the angiographic findings, in-stent restenosis (ISR) was confirmed in 32 cases with a total of 38 lesions (ISR group), while no in-stent restenosis (non-ISR) was seen in 174 cases with a total of 229 lesions (non-ISR group). Before and after the treatment, the cross-sectional area of extra-elastic membrane, plaque area, minimal lumen area (MLA), and intima proliferation area were determined. The changes in MMP-1 and MMP-9 levels after PCI in each group were compared. Based on the MLA, the patients were divided into three groups: MLA > 5 mm 2 group, MLA (3∼5) mm 2 group and MLA 2 group. The MMP-1 and MMP-9 levels were compared among three groups. Results: Both the plaque area and intima proliferation area were significantly larger, while the MLA was significantly smaller, in ISR group than those in non-ISR group (P 5 mm 2 group, MLA (3∼5) mm 2 group and MLA 2 group was (1.45±0.32) ng/ml, (2.93±0.45) ng/ml and (3.09±0.65) ng/ml respectively, but no significant difference in MMP-9 concentration existed between MLA (3∼5) mm 2 group and MLA 2 group (P>0.05). Conclusion: After PCI the increase of MMP-9 concentration bears a close relationship to the degree of restenosis. (authors)

  1. Clinical Coronary In-Stent Restenosis Follow-Up after Treatment and Analyses of Clinical Outcomes

    Directory of Open Access Journals (Sweden)

    Barbara Campos Abreu Marino

    2015-05-01

    Full Text Available Background: Clinical in-stent restenosis (CISR is the main limitation of coronary angioplasty with stent implantation. Objective: Describe the clinical and angiographic characteristics of CISR and the outcomes over a minimum follow-up of 12 months after its diagnosis and treatment. Methods: We analyzed in 110 consecutive patients with CISR the clinical presentation, angiographic characteristics, treatment and combined primary outcomes (cardiovascular death, nonfatal acute myocardial infarction [AMI] and combined secondary (unstable angina with hospitalization, target vessel revascularization and target lesion revascularization during a minimal follow-up of one year. Results: Mean age was 61 ± 11 years (68.2% males. Clinical presentations included acute coronary syndrome (ACS in 62.7% and proliferative ISR in 34.5%. CISR was treated with implantation of drug-eluting stents (DES in 36.4%, Bare Metal Stent (BMS in 23.6%, myocardial revascularization surgery in 18.2%, balloon angioplasty in 15.5% and clinical treatment in 6.4%. During a median follow-up of 19.7 months, the primary outcome occurred in 18 patients, including 6 (5.5% deaths and 13 (11.8% AMI events. Twenty-four patients presented a secondary outcome. Predictors of the primary outcome were CISR with DES (HR = 4.36 [1.44–12.85]; p = 0.009 and clinical treatment for CISR (HR = 10.66 [2.53–44.87]; p = 0.001. Treatment of CISR with BMS (HR = 4.08 [1.75–9.48]; p = 0.001 and clinical therapy (HR = 6.29 [1.35–29.38]; p = 0.019 emerged as predictors of a secondary outcome. Conclusion: Patients with CISR present in most cases with ACS and with a high frequency of adverse events during a medium-term follow-up.

  2. Experimental study on effect of dexamethasone to the in-stent restenosis after vascular intervention

    International Nuclear Information System (INIS)

    Wang Jianbo; Yang Jianyong; Chen Wei; Zhuang Wenquan; Li Jiaping; Zhang Longjuan

    2007-01-01

    Objective: To evaluate the effect of dexamethasone to the cultured rat thoracic aortic smooth muscle cells (SMC) in vitro, and explore the role on it's prevention and cure for the in-stent restenosis after vascular intervention. Methods: The rat thoracic aortic SMC were harvested and cultured for six to ten passages. The cultured SMC were synchronized and then restimutated to enter the cell cycle, and treated with incremental concentrations of dexamethasone or without dexamethasone as control. The proliferative assay was performed with MTT method in the different time points after treatment. RT-PCR was performed to assay the level of proliferating cell nuclear antigen (PCNA) mRNA. Results: 1. Dexamethasone progressively inhibited rat aortic SMC proliferation in a concentration-dependent fashion. The A value was statistically significant for different concentrations (F=36.02, P -6 and 10 -5 mol/L (P=0.065) or between 10 -11 mol/L and control group (P 0.567). 2. RT-PCR suggested dexamethasone significantly decreased rat aortic SMC PCNA mRNA transcription in a concentration-dependent fashion. Statistical analysis indicated F=15.407 and P -9 or 10 -11 mol/L groups by post hoc analysis. Conclusions: Dexamethasone inhibits rat aortic SMC proliferation in a concentration- dependent fashion. The data suggest that effective action concentration is 10 -7 mol/L with persistent time up to 96 hours or more. Dexamethasone may play the inhibit role to SMC at lower concentration with prolonging action time. (authors)

  3. Management of drug eluting stent in-stent restenosis: A systematic review and meta-analysis.

    Science.gov (United States)

    Goel, Sachin S; Dilip Gajulapalli, Rama; Athappan, Ganesh; Philip, Femi; Gupta, Supriya; Murat Tuzcu, E; Ellis, Stephen G; Mishkel, Gregory; Kapadia, Samir R

    2016-05-01

    The optimal management for coronary drug eluting stent in-stent restenosis (DES ISR) is unclear. We performed a meta-analysis of observational and randomized studies to compare the outcomes of management of DES ISR using DES, drug eluting balloon (DEB), or balloon angioplasty (BA). Eligible studies (25 single arm and 13 comparative, including 4 randomized studies with a total of 7,474 patients with DES ISR) were identified using MEDLINE search and proceedings of international meetings. Outcomes studied include major adverse cardiac events (MACE), target lesion revascularization (TLR), target vessel revascularization (TVR), myocardial infarction (MI), stent thrombosis (ST), and mortality. Follow-up ranged from 0.5 to 3.5 years (mean 1.4 years). The rate of TLR was significantly lower in the DES (odds ratio [OR] 0.50, 95% confidence interval [CI] 0.36-0.69) and DEB (OR 0.31, 95% CI 0.18-0.55) groups compared to BA. Similarly, TVR rate was significantly lower in the DES (OR 0.55, 95% CI 0.39-0.77) and DEB (OR 0.32, 95% CI 0.18-0.58) groups compared to BA. All other outcomes were similar between the DES/BA and DEB/BA comparisons. TLR was significantly lower in the DES group compared to BA for vessels  2.75 mm. Treatment of coronary DES ISR with DES or DEB is associated with a reduction in the risk of TLR and TVR compared to BA alone. The relative risk reduction for TLR with DES is similar to DEB. DEBs have a potential role in the treatment of DES ISR by avoiding placement of another layer of stent. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  4. The effect of stent structure changes on the hemodynamics and the formation of in-stent restenosis

    International Nuclear Information System (INIS)

    Wu Xia; Xu Ke; Xiao Liang; Zhang Xitong; Su Hongying; Feng Bo

    2009-01-01

    Objective: To investigate the effect of stent structure changes on the formation of in-stent restenosis by studying the influence of these changes on the shear force to the vascular wall, on the velocity of flow and on the flow pattern. Methods: Five stent models were established by using Pro/engineer wildfire 3.0. Model A was regarded as control structure. On the base structure of model A, transverse link component was added to form model B, and vertical link component was added to form model C. The thickness of model D was twice than that of model A, and the meshes density of model E was twice than that of model A. Fluid models were built up by importing these stent models into computational fluid dynamics (CFD) software ansys11.0-CFX, then, CFD analysis was proceeded to study the effect of stent structure on hemodynamics. Results: After the stents were implanted, the percentage of low wall shear stress on the surface of model A, B, C, D and E was 7.78%, 6.65%, 1.48%, 16.52% and 12.12%, respectively. The percentage of D and E was obviously larger than that of A, while the percentage of B was markedly smaller than that of A. The velocity vector on the cross-sectional planes showed that the low velocity and eddy areas in D and E were much larger than that in A, while this area in C was smaller than that in A. Conclusion: The stent structure changes can cause obvious changes in hemodynamics in the implanted vessels. The increase in the thickness and meshes density of the stent is the main factor that induces the formation of low wall shear stress, which will precipitate the development of in-stent restenosis. The added vertical link component will reduce the area of low wall shear stress as well as the occurrence of in-stent restenosis. (authors)

  5. Safety and efficacy of limus-eluting stents and balloon angioplasty for sirolimus-eluting in-stent restenosis

    Energy Technology Data Exchange (ETDEWEB)

    Ota, Hideaki [Division of Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC 20010 (United States); Mahmoudi, Michael [University of Surrey, Guildford Road, Surrey, GU2-7XH (United Kingdom); Kitabata, Hironori; Torguson, Rebecca; Chen, Fang; Satler, Lowell F.; Suddath, William O.; Pichard, Augusto D. [Division of Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC 20010 (United States); Waksman, Ron, E-mail: ron.waksman@medstar.net [Division of Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC 20010 (United States)

    2015-03-15

    Objectives: The aim of this study was to compare the safety and efficacy of everolimus-eluting stent (EES), sirolimus-eluting stent (SES), and plain old balloon angioplasty (POBA) for the treatment of SES in-stent restenosis (S-ISR). Background: The optimal treatment for drug-eluting in-stent restenosis remains controversial. Methods: The study cohort comprised 310 consecutive patients (444 lesions) who presented with S-ISR to our institution and underwent treatment with EES (43 patients), SES (102), or POBA (165). The analyzed clinical parameters were the 1-year rates of death, Q-wave myocardial infarction (MI), target lesion revascularization (TLR), target vessel revascularization (TVR), definite stent thrombosis (ST) and major adverse cardiac event (MACE) defined as the composite of death, MI, or TLR at 1-year. Results: The three groups were well matched for the conventional risk factors for coronary artery disease except for smoking. The 1-year analyzed clinical parameters were similar in the three groups: MACE (EES = 14%, SES = 18%, POBA = 20%; p = 0.65), death (EES = 2.3%, SES = 6.2%, POBA = 6.1%; p = 0.61), MI (EES = 4.8%, SES = 2.1%, POBA = 2.5%; p = 0.69), TLR (EES = 11.9%, SES = 12.1%, POBA = 24%; p = 0.78), and TVR (EES = 11.9%, SES = 24.8%, POBA = 22.2%; p = 0.23). There were no cases of definite ST. MACE-free rate was significantly lower in patients with recurrent in-stent restenosis (log-rank p = 0.006). Presentation with acute MI, number of treated lesions and a previous history of MI were found to be independent predictors of MACE. Conclusions: In patients presenting with S-ISR, treatment with implantation of an EES, SES, or POBA is associated with similar clinical outcomes. Patients presenting with recurrent ISR may have a poorer clinical outcome.

  6. [Prediction of in-stent restenosis by measurement of fractional flow reserve and the influence of diabetes mellitus].

    Science.gov (United States)

    Amaya, Kazutaka; Takazawa, Kenji; Tanaka, Nobuhiro; Yamashina, Akira

    2002-06-01

    This study tried to predict in-stent restenosis by the measurement of fractional flow reserve and to evaluate the effect of diabetes mellitus control on the relationship between in-stent restenosis and fractional flow reserve. Fractional flow reserve was measured in 62 patients (mean age 61 +/- 9 years, 32 with angina pectoris and 30 with myocardial infarction) after stent implantation. The patients were divided into three groups according to the value of HbA1c and fasting blood sugar (FBS): Group P (HbA1c > or = 6.5% or FBS > or = 126 mg/dl, n = 15), Group G (6.5% > HbA1c > or = 5.8% or 126 > FBS > or = 100 mg/dl, n = 12), and Group N (HbA1c or = 0.90), TLR rate was 60% in Group P, 0% in Group G and 0% in Group N. Fractional flow reserve after stent implantation is useful for the prediction of TLR in patients without diabetes mellitus. However, diabetic control in patients with diabetes mellitus might be attributable to TLR rather than fractional flow reserve.

  7. Brachytherapy using holmium-166 liquid balloon system for in-stent restenosis: 6 months clinical and angiographic follow-up

    Energy Technology Data Exchange (ETDEWEB)

    Kim, M. H.; Kim, S. K.; Cha, K. S.; Kim, Y. D.; Lee, H. S.; Kang, D. Y. [Donga University College of Medicine, Busan (Korea, Republic of)

    2002-07-01

    In western country, 3 systems of brachytherapy using commercial radioactive source has been established. However, brachytherapy using holmium-166 liquid balloon system (HLBS) for the patient with stent restenosis has not been studied enough. 30 patients (male 23, mean age 58.9 7.7) were enrolled. Target dose was 15 Gy at 1 mm distance from the intimal surface. Clinical diagnoses of the study patients included stable angina 10 and unstable angina 20 patients. Target lesion included LAD 19, LCx 5 and RCA 6 arteries. Pre-brachytherapy treatment included cutting balloon angioplasty in 25, rotational atherectomy in 5 patients. Fractionation and stepping was done in 6 patients each. Follow-up angiography was done in 19 patients. Of them, 4 cases developed angiographic restenosis (21%) including 3 cases of total occlusion. 6 month MACE (major adverse cardiac event) occurred in 5 patients including one sudden cardiac death in a patient with 80 year-old, triple-vessel diseased patient. Vascular brachytherapy using HLBS is a safe and effective treatment modality for in-stent restenosis showing acceptable angiographic and clinical result.

  8. No association between metal allergy and cardiac in-stent restenosis in patients with dermatitis-results from a linkage study.

    Science.gov (United States)

    Thyssen, Jacob P; Engkilde, Kåre; Menné, Torkil; Johansen, Jeanne D; Hansen, Peter Riis; Gislason, Gunnar H

    2011-03-01

    Percutaneous coronary intervention (PCI) with implantation of a metal stent is a common procedure performed in patients with symptomatic ischaemic heart disease. Intracoronary stents typically have a backbone of stainless steel, which contains nickel, chromium, and molybdenum, and it remains unclear whether individuals who are allergic to these metals have an increased risk of restenosis after PCI with stent implantation. To further evaluate whether dermatitis patients with nickel and/or chromium allergy had an increased risk of developing cardiac in-stent restenosis with stainless steel stents. An individual-level linkage study was performed to identify dermatitis patients who had been patch tested with the European baseline series between 1979 and 2007 at Gentofte University Hospital (N = 18794) and who had also undergone PCI at some point in a Danish hospital. One hundred and forty-nine (0.8%) dermatitis patients who had undergone PCI with a metal stent were included. One hundred and forty-seven were patch-tested before undergoing PCI. Of the patients, 14.1% (21/149) had cardiac in-stent restenosis. Among patients with metal allergy, 2 (11.8%) had restenosis. Nickel and/or chromium allergy in dermatitis patients does not appear to increase the overall risk of in-stent restenosis after PCI. © 2011 John Wiley & Sons A/S.

  9. Dexamethasone-eluting stents for the prevention of in-stent restenosis: Evidence for a differential effect in insulin-dependent and non-insulin-dependent diabetic patients

    NARCIS (Netherlands)

    Hoeven, B.L. van der; Pires, N.M.M.; Warda, H.M.; Putter, H.; Quax, P.H.A.; Schalij, M.J.; Jukema, J.W.

    2008-01-01

    Diabetes mellitus (DM) is a strong predictor of in-stent restenosis. This may be due to a higher level of vascular inflammation. We hypothesized that diabetic patients will benefit from dexamethasone-eluting stents, since local inflammation and consequently neointimal growth are suppressed and no

  10. In-stent restenosis and multislice computed tomography: is the method ready to start?

    Science.gov (United States)

    Martuscelli, Eugenio; Razzini, Cinzia; D'Eliseo, Alessia; Di Luozzo, Marco; Mauro, Borzi; Romeo, Francesco

    2007-05-01

    We present two patients revascularized by coronary stents and evaluated by multislice computed tomography (CT). In first patient, angio-CT (16 slices/rotation scanner) detected a high-grade restenosis on the distal part of a drug-eluting stent; conventional coronary angiography confirmed the diagnosis. In second patient, angio-CT (64 slices/rotation) showed a tissue proliferation, non-flow-limiting, in the proximal part of a bare metal stent; conventional angiography confirmed the diagnosis. Blooming effects and partial volume averaging still limit the widespread application of this method. New scanners and the use of a special convolution kernel are likely to improve the accuracy of CT angiography in patients with stents.

  11. Influence of Vessel Size and Tortuosity on In-stent Restenosis After Stent Implantation in the Vertebral Artery Ostium

    International Nuclear Information System (INIS)

    Zhou Zhiming; Yin Qin; Xu Gelin; Yue Xuanye; Zhang Renliang; Zhu Wusheng; Fan Xiaobing; Ma Minmin; Liu Xinfeng

    2011-01-01

    Purpose: Percutaneous transluminal angioplasty and stenting is emerging as an alternative for treating atherosclerotic stenosis in the vertebral artery ostium. However, in-stent restenosis (ISR) still remains a critical issue to be addressed. Little is known about the relationship between anatomic characteristics of the artery and ISR after stent implantation. In this study, we have evaluated influential factors for ISR in a cohort of the patients with stenting in the vertebral artery ostium. Methods: Sixty-one patients with 63 symptomatic lesions in vertebral artery ostium treated with stenting were enrolled onto this study. An average of 12.5 months’ clinical and angiographic follow-up results were analyzed retrospectively. The possible influential factors for ISR, including conventional risk factors of cerebrovascular diseases and morphological characteristics of target lesions, were evaluated by univariate and multivariate regression analysis. Results: Technical success was achieved in all 63 interventional procedures. Stenosis was reduced from (mean ± standard deviation) 75.5 ± 12% before to 1 ± 3.6% after the procedure. During the mean 12.5-month angiographic follow-up, ISR was detected in 17 treated vessels (27.0%), with 2 treated arteries (3.2%) resulting in occlusion, and a stent fracture in 1 case (1.6%). Multivariate Cox regression analysis showed that the tortuosity of V1 (hazard ratio 3.54, P = 0.01) and smaller diameter of the stent (hazard ratio 3.8, P = 0.04) were independent predictors of ISR. Conclusions: Angioplasty and stenting for symptomatic stenosis in the vertebral artery ostium stenosis seem to be feasible and effective. Tortuosity and smaller diameter may affect ISR after stent implantation.

  12. Risk factors for in-stent restenosis of vertebral artery origin after stent implantation: a Meta-analysis

    Directory of Open Access Journals (Sweden)

    Fang-fang HAO

    2018-01-01

    Full Text Available Objective To systematically review the risk factors for in-stent restenosis (ISR of vertebral artery origin after sent implantation to provide theoretical foundation for clinical prevention and treatment. Methods Taking vertebral artery, vertebrobasilar insufficiency, stents, drug-eluting stents, self expandable metallic stents in English and Chinese as key words, retrospective clinical studies about risk factors for ISR of vertebral artery origin were searched by using PubMed, EMBASE/SCOPUS, Cochrane Library, China Biology Medicine (CBM, China National Knowledge Infrastructure (CNKI, Wanfang Data and VIP database from January 1, 1966 to March 30, 2017. Quality assessment and Meta-analysis were made by using Newcastle-Ottawa Scale (NOS and Stata 12.0 software. Results The research enrolled 3468 articles in all, from which 11 studies were chosen after excluding duplicates and those not meeting the inclusion criteria. A total number of 1352 patients were divided into ISR group (N = 440 and non-ISR group (N = 912. The ISR incidence rate of smokers was significantly higher than non-smokers (OR = 2.179, 95%CI: 1.373-3.458; P = 0.001. The differences of bare metal stents (BMS utilization rate (OR = 2.072, 95% CI: 1.560-2.753; P = 0.000 and drug-eluting stents (DES utilization rate (OR = 0.483, 95% CI: 0.363-0.641; P = 0.000 between ISR group and non-ISR group were statistically significant. Conclusions Smoking and using BMS are risk factors for ISR of vertebral artery origin, and using DES is protective factor. Due to limited study quality, more high-quality studies are needed to verify this conclusion. DOI: 10.3969/j.issn.1672-6731.2017.12.004

  13. Is there a link between nickel allergy and coronary stent restenosis?

    Science.gov (United States)

    Norgaz, Tugrul; Hobikoglu, Gultekin; Serdar, Zehra Asiran; Aksu, Huseyin; Alper, Ahmet Taha; Ozer, Orhan; Narin, Ahmet

    2005-07-01

    Although many patients with coronary artery disease are being treated by coronary stents, in-stent restenosis is the major limitation of percutaneous coronary stenting procedures. Most stents are made of stainless steel, and that, allergic reactions to nickel ions released from coronary stainless-steel stents may be one of the triggering mechanisms for in-stent restenosis. We aimed to evaluate the relationship between in-stent restenosis and nickel allergy in a prospective study. For this purpose, we applied epicutaneous patch test for nickel in 43 patients who had undergone elective intracoronary stent placement for stable angina pectoris in the day following stent placement and evaluated the presence of nickel allergy. Control angiography was performed at 6 months to determine in-stent restenosis. Three (6.9%) patients had allergic reaction to nickel and 16 (37%) patients had developed in-stent restenosis. One of the 3 patients with nickel allergy had diffuse in-stent restenosis and the others not. The present study therefore does not support the proposed relationship between nickel allergy and development of in-stent restenosis in patients having stainless steel stents. Large scale studies are needed to reach a final conclusion.

  14. Prospective ECG-triggered axial CT at 140-kV tube voltage improves coronary in-stent restenosis visibility at a lower radiation dose compared with conventional retrospective ECG-gated helical CT

    Energy Technology Data Exchange (ETDEWEB)

    Horiguchi, Jun; Fujioka, Chikako; Kiguchi, Masao; Kohno, Shingo [Hiroshima University Hospital, Department of Clinical Radiology, Hiroshima (Japan); Yamamoto, Hideya; Kitagawa, Toshiro [Hiroshima University, Department of Molecular and Internal Medicine, Division of Clinical Medical Science, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima (Japan); Ito, Katsuhide [Hiroshima University, Department of Radiology, Division of Medical Intelligence and Informatics, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima (Japan)

    2009-10-15

    The purpose of this study was to compare coronary 64-slice CT angiography (CTA) protocols, specifically prospective electrocardiograph (ECG)-triggered and retrospective ECG-gated CT acquisition performed using a tube voltage of 140 kV and 120 kV, regarding intracoronary stent imaging. Coronary artery stents (n=12) with artificial in-stent restenosis (50% luminal reduction, 40 HU) on a cardiac phantom were examined by CT at heart rates of 50-75 beats per minute (bpm). The subjective visibility of in-stent restenosis was evaluated with a three-point scale (1 clearly visible, 2 visible, and 3 not visible), and artificial lumen narrowing [(inner stent diameter - measured lumen diameter)/inner stent diameter], lumen attenuation increase ratio [(in-stent attenuation - coronary lumen attenuation)/coronary lumen attenuation], and signal-to-noise ratio of in-stent lumen were determined. The effective dose was estimated. The artificial lumen narrowing (mean 43%), the increase of lumen attenuation (mean 46%), and signal-to-noise ratio (mean 7.8) were not different between CT acquisitions (p=0.12-0.91). However, the visibility scores of in-stent restenosis were different (p<0.05) between ECG-gated CTA techniques: (a) 140-kV prospective (effective dose 4.6 mSv), 1.6; (b) 120-kV prospective (3.3 mSv), 1.8; (c) 140-kV retrospective (16.4-18.8 mSv), 1.9; and (d) 120-kV retrospective (11.0-13.4 mSv), 1.9. Thus, 140-kV prospective ECG-triggered CTA improves coronary in-stent restenosis visibility at a lower radiation dose compared with retrospective ECG-gated CTA. (orig.)

  15. Intracoronary local paclitaxel delivery by X-ray contrast media for in-stent restenosis: a clinical pilot study to assess safety and tolerability.

    Science.gov (United States)

    Rutsch, W; Scheller, B; Borges, A C; Bräutigam, M; Clever, Y; Cremers, B; Dietz, U; Richter, W; Speck, U

    2012-08-01

    Non-stent-based immediate release formulations of paclitaxel have been shown to reduce in-stent restenosis in animal experiments and clinical trials. In the porcine overstretch model paclitaxel dissolved in the contrast medium iopromide inhibited neointimal proliferation in a dose-dependent manner after intracoronary injection and was well tolerated. As a first step entering clinical development, a phase I trial was performed using four ascending paclitaxel dose/concentration levels: samples of up to 100 mL of the contrast medium (iopromide) containing 10, 50, 100 or 200 µM paclitaxel or iopromide (controls) were randomly administered to patients assigned to bare metal stent implantation for single de novo coronary artery lesions. Safety variables, tolerability and angiographic parameters were assessed. Adverse events, ECG, systolic and diastolic blood pressure, left ventricular ejection fraction, leukocyte count, other hematological or clinical chemistry data did not reveal any trend which could be related to the study medication. Short-lasting serum paclitaxel concentrations remained significantly below those known from cancer therapy. Angiographic late lumen loss was 0.72±0.50 mm (N.=7) in controls versus 0.45±0.65 mm (N.=17) in all paclitaxel-treated patients; binary restenosis rate was 5/7(63%) versus 6/17 (35%) and target lesion revascularization rate was 4/8 (50%) versus 4/24 (17%). Intracoronary infusion of paclitaxel dissolved in an X-ray contrast medium was well tolerated. The results show restenosis inhibition, but the number of patients examined was too small to demonstrate a statistically significant inhibition.

  16. Effect of pioglitazone on in-stent restenosis after coronary drug-eluting stent implantation: a meta-analysis of randomized controlled trials.

    Directory of Open Access Journals (Sweden)

    Ming-duo Zhang

    Full Text Available In-stent restenosis (ISR remains a common life-threatening complication and some studies have shown that pioglitazone can reduce the incidence of ISR in patients with drug-eluting stents (DES implantation. We conducted a meta-analysis to assess the effect of pioglitazone in preventing ISR after DES implantation.Randomized controlled trials (RCTs investigating the effects of pioglitazone for ISR after DES implantation were identified by systematic searches of multiple online databases and manual searches of related reference lists of identified trials through May 2014. The primary endpoint was the rate of ISR. Secondary endpoints included minimum lumen diameter, percentage stenosis of stented vessels, late loss, in-stent neointimal volume, target vessel revascularization (TVR, target lesion revascularization, myocardial infarction, stent thrombosis and death.Five studies, comprising 255 pioglitazone-treated patients and 245 controls, were identified in the current meta-analysis. Pioglitazone did not significantly reduce the rate of ISR (P = 0.20 with low heterogeneity (I2 = 13.3%, P = 0.32. For the secondary outcomes, pioglitazone did not substantially affect the pooled estimates of these endpoints except late loss (P = 0.01 and TVR (P = 0.04.The limited evidence indicates that pioglitazone does not demonstrate markedly beneficial effect in patients subjected to coronary DES implantation. However, the results should be interpreted with care given the small sample size. Further large-scale RCTs are needed.

  17. Incidence and classification of neointimal proliferation and in-stent restenosis in post-stenting patients at 1-year interval: Findings from non-invasive coronary computed tomography angiography

    International Nuclear Information System (INIS)

    Xu, Nan; Zhang, Jiayin; Li, Minghua; Pan, Jingwei; Lu, Zhigang

    2014-01-01

    Highlights: • The incidence of silent in-stent restenosis at 1-year as revealed by CT is 7.6%. • The incidence of neointimal proliferation at 1-year as revealed by CT is 12.6%. • Diabetes are associated with higher incidence of neointimal proliferation. - Abstract: Objectives: To evaluate the incidence of coronary in-stent restenosis (ISR) and neointimal proliferation by coronary CT angiography (CCTA) at 1-year follow-up in asymptomatic patients. Methods: 234 patients (mean age: 67 ± 10.2 years, range 39–88 years, 180 males and 54 females) with 379 stents were prospectively enrolled in this study. Binary ISR was classified by CCTA into 4 types using Mehran classification. Neointimal proliferation was similarly classified into focal and diffuse types. All patients with CCTA-revealed ISR or neointimal proliferation underwent further invasive coronary angiography (ICA) for validation. Fisher's exact test was used for comparison. Results: ICA revealed patent stents with neointimal proliferation in 39 patients (16.7%, 39/234) and binary ISR in 23 patients (9.8%, 23/234). Lesion-based analysis showed 12 type I ISR lesions, 4 type II ISR lesions, 1 type III ISR lesion and 7 type IV ISR lesions. Among cases with neointimal proliferation, 27 lesions were classified as focal type whereas 13 lesions were classified as diffuse type. Patients with diabetes mellitus were associated with higher incidence of CCTA-revealed neointimal proliferation (21/77 vs. 18/157, p = 0.002) as well as ISR (12/77 vs. 11/157, p = 0.038), compared to patients without diabetes. CCTA was found to have good diagnostic performance for neointimal proliferation and ISR detection as well as classification, with an overall accuracy of 84.4% (54/64). Conclusions: Silent ISR as well as neointimal proliferation is not uncommon findings in asymptomatic post-stenting patients at 1-year interval, as revealed by CCTA. Patients with diabetes are prone to have higher incidence of neointimal

  18. Incidence and classification of neointimal proliferation and in-stent restenosis in post-stenting patients at 1-year interval: Findings from non-invasive coronary computed tomography angiography

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Nan, E-mail: southmuch@hotmail.com [Department of Radiology, East Hospital, Tongji University School of Medicine, No. 150, Jimo Road, Shanghai 200120 (China); Zhang, Jiayin, E-mail: andrewssmu@msn.com [Department of Radiology, Shanghai Jiao Tong University Affiliated Sixth People' s Hospital, No. 600, Yishan Road, Shanghai 200233 (China); Li, Minghua, E-mail: drliminghua@gmail.com [Department of Radiology, Shanghai Jiao Tong University Affiliated Sixth People' s Hospital, No. 600, Yishan Road, Shanghai 200233 (China); Pan, Jingwei, E-mail: drpanjingwei@gmail.com [Department of Cardiology, Shanghai Jiao Tong University Affiliated Sixth People' s Hospital, No. 600, Yishan Road, Shanghai 200233 (China); Lu, Zhigang, E-mail: drluzhigang@gmail.com [Department of Cardiology, Shanghai Jiao Tong University Affiliated Sixth People' s Hospital, No. 600, Yishan Road, Shanghai 200233 (China)

    2014-10-15

    Highlights: • The incidence of silent in-stent restenosis at 1-year as revealed by CT is 7.6%. • The incidence of neointimal proliferation at 1-year as revealed by CT is 12.6%. • Diabetes are associated with higher incidence of neointimal proliferation. - Abstract: Objectives: To evaluate the incidence of coronary in-stent restenosis (ISR) and neointimal proliferation by coronary CT angiography (CCTA) at 1-year follow-up in asymptomatic patients. Methods: 234 patients (mean age: 67 ± 10.2 years, range 39–88 years, 180 males and 54 females) with 379 stents were prospectively enrolled in this study. Binary ISR was classified by CCTA into 4 types using Mehran classification. Neointimal proliferation was similarly classified into focal and diffuse types. All patients with CCTA-revealed ISR or neointimal proliferation underwent further invasive coronary angiography (ICA) for validation. Fisher's exact test was used for comparison. Results: ICA revealed patent stents with neointimal proliferation in 39 patients (16.7%, 39/234) and binary ISR in 23 patients (9.8%, 23/234). Lesion-based analysis showed 12 type I ISR lesions, 4 type II ISR lesions, 1 type III ISR lesion and 7 type IV ISR lesions. Among cases with neointimal proliferation, 27 lesions were classified as focal type whereas 13 lesions were classified as diffuse type. Patients with diabetes mellitus were associated with higher incidence of CCTA-revealed neointimal proliferation (21/77 vs. 18/157, p = 0.002) as well as ISR (12/77 vs. 11/157, p = 0.038), compared to patients without diabetes. CCTA was found to have good diagnostic performance for neointimal proliferation and ISR detection as well as classification, with an overall accuracy of 84.4% (54/64). Conclusions: Silent ISR as well as neointimal proliferation is not uncommon findings in asymptomatic post-stenting patients at 1-year interval, as revealed by CCTA. Patients with diabetes are prone to have higher incidence of neointimal

  19. Neoatherosclerosis causing occlusive in-stent restenosis: Impact of intracoronary imaging in the intensity of lipid-lowering therapy

    Energy Technology Data Exchange (ETDEWEB)

    Martí, David, E-mail: docalcala@hotmail.com [Department of Cardiology, Hospital Central de la Defensa, Madrid (Spain); López, Edurne; Álvarez, Salvador; Palazuelos, Jorge; Rada, Ignacio [Department of Cardiology, Hospital Central de la Defensa, Madrid (Spain); Alfonso, Fernando [Department of Cardiology, Hospital Universitario de La Princesa, Madrid (Spain)

    2016-12-15

    The unique physical properties of optical coherence tomography (OCT) make it a useful technique in the study of restenosis mechanisms. In fact, OCT is able to differentiate between neointimal proliferation and neoatherosclerosis within the stent. We report a rare case of occlusive neoatherosclerosis presenting beyond one year after a successful drug-eluting stent implantation. The impact of OCT findings in the clinical decision making process is emphasized. - Highlights: • Optical coherence tomography (OCT) has the unique ability to detect lipid accumulation within the stent margins (i.e. neoatherosclerosis). • Lipid-rich tissues produce light absorption and therefore they typically attenuate backward signals. • Occlusive neoatherosclerosis may appear even in optimally implanted drug eluting stents. • OCT identification of restenosis mechanisms may have implications not only in the interventional strategy, but also in the long-term medical treatment.

  20. [Vertebral-subclavian bifurcation treatment. "The wedding ring technique" for a vertebral in-stent restenosis associated with stent fracture].

    Science.gov (United States)

    Damas-De Los Santos, Félix; Colombo, Federico; Zuffi, Andrea; Cremonesi, Alberto

    2015-01-01

    This report describes a solution for a restenosis and for the fracture of a stent in the vertebral artery in a patient suffering from vertebrobasilar symptoms. Angiography demonstrates restenosis of a vertebral stent as well as its fracture and migration into the subclavian artery. This complication was managed percutaneously by passing a guide wire through the fractured stent. Pre-dilatation and kissing balloon techniques were applied in both the vertebral and subclavian arteries to modify the stent's dimensions and shape it into the form of a "ring." Postprocedural angiography demonstrated an excellent final result with the assistance of StentBoost visualization. Control angiography at six months also utilized StentBoost imaging and confirmed the patency of the bifurcation and that the stent was not displaced.

  1. Drug-Coated Balloon Treatment for Femoropopliteal Artery Disease: The IN.PACT Global Study De Novo In-Stent Restenosis Imaging Cohort.

    Science.gov (United States)

    Brodmann, Marianne; Keirse, Koen; Scheinert, Dierk; Spak, Lubomir; Jaff, Michael R; Schmahl, Randy; Li, Pei; Zeller, Thomas

    2017-10-23

    This study sought to evaluate the safety and effectiveness of a paclitaxel-coated drug-coated balloon (DCB) for the treatment of patients with de novo in-stent restenosis (ISR). Treatment of patients with ISR remains a challenge. Current strategies are plagued by high rates of recurrent restenosis and need for reintervention. The best intervention for ISR remains to be elucidated. The IN.PACT Global study is an independently adjudicated multicenter, prospective, single-arm study that enrolled 1,535 subjects with symptomatic atherosclerotic disease of the superficial femoral and/or popliteal arteries, including de novo ISR lesions. Patients enrolled in the pre-specified ISR imaging cohort were evaluated for vessel patency and reintervention within the 12-month follow-up period. A total of 131 subjects with 149 ISR lesions were included for analysis. The mean age of the cohort was 67.8 years. Mean lesion length was 17.17 ± 10.47 cm, including 34.0% total occlusions and 59.1% calcified lesions. The 12-month Kaplan-Meier estimate of primary patency was 88.7%. The rate of clinically driven target lesion revascularization (CD TLR) at 12 months was 7.3%. The primary safety outcome, a composite of freedom from device- and procedure-related mortality through 30 days and freedom from major target limb amputation and CD TLR within 12 months, was 92.7%. There were no major target limb amputations, no deaths, and a low (0.8%) thrombosis rate. Results from the ISR imaging cohort demonstrate high patency and a low rate of CD TLR at 12 months. These data confirm the safety and effectiveness of the IN.PACT Admiral DCB (Medtronic, Dublin, Ireland) in complex femoropopliteal lesions, including this challenging subset. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  2. The SABRE Trial (Sirolimus Angioplasty Balloon for Coronary In-Stent Restenosis): Angiographic Results and 1-Year Clinical Outcomes.

    Science.gov (United States)

    Verheye, Stefan; Vrolix, Mathias; Kumsars, Indulis; Erglis, Andrejs; Sondore, Dace; Agostoni, Pierfrancesco; Cornelis, Kristoff; Janssens, Luc; Maeng, Michael; Slagboom, Ton; Amoroso, Giovanni; Jensen, Lisette Okkels; Granada, Juan F; Stella, Pieter

    2017-10-23

    The aim of this first-in-human study was to assess the safety and effectiveness of the Virtue sirolimus-eluting balloon in a cohort of patients with in-stent restenosis (ISR). Angioplasty balloons coated with the cytotoxic drug paclitaxel have been widely used for ISR treatment. The Virtue angioplasty balloon (Caliber Therapeutics, New Hope, Pennsylvania) delivers sirolimus in a nanoencapsulated liquid formulation. This clinical trial is the first to examine a sirolimus-eluting balloon for ISR. In this prospective, single-arm feasibility study at 9 European centers, 50 ISR patients were treated with the Virtue balloon. Angiographic measurements at 6 months are reported, along with 12-month clinical follow-up. Procedural success in the intention-to-treat population was 100%. The primary safety endpoint was target lesion failure (TLF) (cardiac death, target vessel myocardial infarction, and clinically driven target lesion revascularization) assessed at 30 days (0%, n = 50). The primary performance endpoint was in-segment late lumen loss (LLL) at 6 months (0.31 ± 0.52 mm; n = 47). Secondary 6-month endpoints include binary restenosis (19.1%), diameter stenosis (30.3 ± 19.9%), and major adverse cardiac events (MACE) (10.2%, n = 49). In the 36-patient per-protocol population (excluding major protocol violations and previously stented ISR), LLL was 0.12 ± 0.33 mm at 6 months. Clinical outcomes at 1 year for the intention-to-treat group were 12.2% TLF and 14.3% MACE and for the per-protocol population were 2.8% TLF and 2.8% MACE. This first-in-human study showed excellent procedural success for the Virtue sirolimus-eluting angioplasty balloon, 6-month LLL rates in line with current stent-free ISR treatment options, and clinical outcomes that warrant further evaluation in dedicated randomized studies. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  3. Second-generation drug-eluting stents versus drug-coated balloons for the treatment of coronary in-stent restenosis: A systematic review and meta-analysis.

    Science.gov (United States)

    Kokkinidis, Damianos G; Prouse, Andrew F; Avner, Seth J; Lee, Joo Myung; Waldo, Stephen W; Armstrong, Ehrin J

    2017-10-10

    The benefit of drug-eluting stents (DES) versus drug-coated balloons (DCB) in coronary artery in-stent restenosis (ISR) for the prevention of target lesion revascularization (TLR), stent thrombosis, and mortality remains uncertain. Our aim was to synthesize the available evidence from randomized clinical trials (RCTs) and observational studies that directly compare second-generation drug-eluting stents (SG-DES) and DCB for the treatment of coronary ISR. Medline, Embase, and Cochrane Central were searched for RCTs or observational studies, published up to March 15, 2017. A random effects model meta-analysis investigating clinical and angiographic outcomes was conducted for RCTs and observational studies that compared SG-DES versus DCB for the treatment of ISR. Ten studies and 2,173 patients were included in this meta-analysis. The two treatment strategies were proven equal with regards to TLR, myocardial infarction, stent thrombosis, and cardiac mortality in both randomized and observational studies. No difference was found among RCTs for all-cause mortality, while in observational studies, patients who were treated with SG-DES had a lower mortality compared to DCB (OR: 0.47; 95% CI: 0.27-0.83). In the pooled analysis also (RCTs and observational studies), SG-DES were associated with lower all-cause mortality compared to DCB. Patients treated with SG-DES were also superior in terms of minimal lumen diameter (standardized mean difference: 0.39; 95% CI: 0.12-0.66). The two treatment strategies are equal for the treatment of ISR, while the difference in all-cause mortality might be potentially explained by baseline differences in the two groups among real-world studies. © 2017 Wiley Periodicals, Inc.

  4. Comparison of drug-eluting balloon versus drug-eluting stent treatment of drug-eluting stent in-stent restenosis: A meta-analysis of available evidence.

    Science.gov (United States)

    Bajraktari, Gani; Jashari, Haki; Ibrahimi, Pranvera; Alfonso, Fernando; Jashari, Fisnik; Ndrepepa, Gjin; Elezi, Shpend; Henein, Michael Y

    2016-09-01

    In-stent restenosis (ISR) remains an important concern despite the recent advances in the drug-eluting stent (DES) technology. The introduction of drug-eluting balloons (DEB) offers a good solution to such problem. We performed a meta-analysis to assess the clinical efficiency and safety of DEB compared with DES in patients with DES-ISR. A systematic search was conducted and all randomized and observational studies which compared DEB with DES in patients with DES-ISR were included. The primary outcome measure-major adverse cardiovascular events (MACE)-as well as individual events as target lesion revascularization (TLR), stent thrombosis (ST), myocardial infarction (MI), cardiac death (CD) and all-cause mortality, were analyzed. Three randomized and 4 observational studies were included with a total of 2052 patients. MACE (relative risk [RR]=1.00, 95% confidence interval (CI) 0.68 to 1.46, P=0.99), TLR (RR=1.15 [CI 0.79 to 1.68], P=0.44), ST (RR=0.37[0.10 to 1.34], P=0.13), MI (RR=0.97 [0.49 to 1.91], P=0.93) and CD (RR=0.73 [0.22 to 2.45], P=0.61) were not different between patients treated with DEB and with DES. However, all-cause mortality was lower in patients treated with DEB (RR=0.45 [0.23 to 0.87, P=0.019) and in particular when compared to only first generation DES (RR 0.33 [0.15-0.74], P=0.007). There was no statistical evidence for publication bias. The results of this meta-analysis showed that DEB and DES have similar efficacy and safety for the treatment of DES-ISR. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  5. Drug-eluting balloons versus drug-eluting stents for the management of in-stent restenosis: A meta-analysis of randomized and observational studies.

    Science.gov (United States)

    Wang, Yanwei; Lou, Xinmin; Xu, Xiaomin; Zhu, Jianhua; Shang, Yunpeng

    2017-11-01

    The aim of this study was to evaluate the efficacy of drug-eluting balloons (DEB) with drug-eluting stents (DES) in patients with in-stent restenosis (ISR). DES implantation and DEB were available strategies in percutaneous coronary intervention (PCI) for ISR, but the optimal management for ISR lesions remains controversial. Electronic databases were searched for randomized controlled trials and observational cohort studies which reported the clinical outcomes of using DEB comparing with DES implantation in patients with ISR. Clinical endpoints such as major adverse cardiovascular events (MACE), death, and myocardial infarction were assessed. Five randomized controlled trials and five observational cohort studies with 962 patients in the DEB group and 908 patients in the DES group met inclusion criteria. There was no significant difference between DEB and DES in major clinical outcomes, such as MACE (OR 1.01; 95% CI: 0.64-1.58; p=0.97; I 2 =0%), all-cause death (OR 1.04; 95% CI: 0.54-1.98; p=0.91; I 2 =0%), cardiovascular death (OR 1.44; 95% CI: 0.57-3.65; p=0.44; I 2 =0%), stent thrombosis (OR 0.61; 95% CI: 0.16-2.33; p=0.47; I 2 =0%), and myocardial infarction (OR 1.02; 95% CI: 0.53-1.94; p=0.96; I 2 =0%). DEB was associated with a significant increase in target lesion revascularization (OR 1.54; 95% CI: 1.10-2.15; p=0.01; I 2 =57%). Treatment of ISR using DEB led to comparable clinical outcomes with DES implantation. Copyright © 2017 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

  6. Evaluation of coronary in-stent restenosis by 64-slice computed tomography in patients with optimal heart rate control by systematic administration of beta-blocker drugs.

    Science.gov (United States)

    Martuscelli, Eugenio; Romagnoli, Andrea; D'eliseo, Alessia; Sperandio, Massimiliano; Di Luozzo, Marco; De Angelis, Barbara; Romeo, Francesco; Simonetti, Giovanni

    2010-06-01

    Imaging artifacts due to metallic stent struts can reduce the diagnostic accuracy of multislice computed tomography (MSCT) in the evaluation of in-stent restenosis (ISR). Our aim was to determine the accuracy of binary ISR exclusion using a 64-slice MSCT scanner and a systematic administration of beta-blockers having an aggressive heart rate (HR) control. We performed 64-slice MSCT in 218 consecutive patients revascularized by stenting. All patients were treated with oral/intravenous beta-blocker drugs in order to obtain a HR less than 65 beats/min in the prescan phase. Coronary stents were evaluated by two experienced observers in order to rule out the presence of significant (>50%) ISR. Quantitative conventional coronary angiography (CCA) served as a standard for reference. Five patients (2.3%) were excluded from the analysis; mean HR was 59 +/- 3 beats/min in the prescan phase and 62 +/- 5 beats/min during acquisition. In the 321 stented coronary segments, CCA found 27 significant ISRs. MSCT correctly diagnosed 26 significant ISRs, with two false-positive and one false-negative case. In a per-segment analysis, the sensitivity was 96%, specificity 99%, positive predictive value (PPV) 92.8%, and negative predictive value (NPV) 99%. In a per-patient analysis, the sensitivity was 100%, specificity 98.9%, PPV 92.8%, and NPV 100%. In our study, the evaluation of significant ISR by MSCT showed an excellent diagnostic accuracy with a PPV of 92.8% and a NPV of 99%. Selection criteria and radiation exposure can be considered a limitation of the method.

  7. Serum Level of Interleukin-18 to Interleukin-10 Ratio after Percutaneous Coronary Intervention: A New Predictor of In-Stent Restenosis

    Directory of Open Access Journals (Sweden)

    Nozar Givtaj

    2016-10-01

    Full Text Available Despite advanced techniques of stent placement which cause fewer traumas to the vessel walls; as well as introduction of drug-eluting stents which result in the least induction of immune response, in-stent restenosis (ISR is still one of the common and severe complications after PCI and stent placement. Intimal hyperplasia following immuno- inflammatory response of the arterial wall to balloon injury has been proposed as main mechanism of ISR. In a prospective study, we assessed the predictive role of Interleukin (IL-18 and tumor necrosis factor alpha (TNF-α as pro-inflammatory cytokines and IL-10 as anti-inflammatory cytokine and high sensitive C-reactive protein (hs-CRP for ISR. 128 patients (mean age=59±10.2, female/male: 41/87who underwent percutaneous coronary intervention (PCI and stent implantation. Venous blood samples were obtained before and 24 hours after PCI. IL-18, IL-10, TNF-αand hs-CRP levels were determined. We followed the patients for 24 months and measured the incidence of ISR via angiography. Results were compared between ISR and non-ISR patients. 20 patients (15.6% developed ISR. Serum level of IL-18, TNF-α and hs-CRP have been increased in all patients 24 hours after PCI. Serum level of IL-18 at 24-hours was not different between ISR and non-ISR patients (p=0.239, while serum level of IL-10 was significantly higher in non-ISR group (p<0.001. IL-18/IL-10 was significantly higher in ISR patients than in non-ISR patients (p<0.001. IL-18/IL-10 can be applied as predictive factors for ISR.

  8. Drug-Eluting Balloon versus New-Generation Drug-Eluting Stent for the Treatment of In-Stent Restenosis: An Updated Systematic Review and Meta-Analysis.

    Science.gov (United States)

    Cui, Kong-Yong; Lyu, Shu-Zheng; Zhang, Min; Song, Xian-Tao; Yuan, Fei; Xu, Feng

    2018-03-05

    Currently, drug-eluting balloon (DEB) appears to be an attractive alternative option for the treatment of in-stent restenosis (ISR). Nevertheless, the clinical outcomes of DEB have seldom been compared to those of new-generation drug-eluting stent (DES). Thus, this meta-analysis aimed to evaluate the safety and efficacy of DEB compared to those of new-generation DES in the treatment of ISR. A comprehensive search of electronic databases including PubMed, EMBASE, and Cochrane Library up to November 2, 2017 was performed to identify pertinent articles comparing DEB to new-generation DES for the treatment of ISR. In addition, conference proceedings for the scientific sessions of the American College of Cardiology, American Heart Association, European Society of Cardiology, Transcatheter Cardiovascular Therapeutics, and EuroPCR were also searched. The primary endpoint was target lesion revascularization (TLR) at the longest follow-up. Dichotomous variables were presented as risk ratios (RR s) with 95% confidence intervals (CI s), while the overall RR s were estimated using the Mantel-Haenszel random-effects model. Five randomized controlled trials (RCTs) and eight observational studies involving 2743 patients were included in the present meta-analysis. Overall, DEB was comparable to new-generation DES in terms of TLR (RR = 1.24, 95% CI: 0.89-1.72, P = 0.21), cardiac death (RR = 1.55, 95% CI: 0.89-2.71, P = 0.12), major adverse cardiovascular event (RR = 1.21, 95% CI: 0.98-1.48, P = 0.07), myocardial infarction (RR = 1.12, 95% CI: 0.72-1.76, P = 0.62), and stent thrombosis (RR = 0.95, 95% CI: 0.38-2.42, P = 0.92). However, DEB was associated with higher risk of all-cause mortality than new-generation DES (RR = 1.65, 95% CI: 1.09-2.50, P = 0.02). This was especially true in the real-world observational studies (RR = 1.79, 95% CI: 1.12-2.88, P = 0.02). In RCTs, however, no significant difference was found between the two treatment strategies in the risk of all

  9. Comparison of new-generation drug-eluting stents versus drug-coated balloon for in-stent restenosis: a meta-analysis of randomised controlled trials.

    Science.gov (United States)

    Cai, Jin-Zan; Zhu, Yong-Xiang; Wang, Xin-Yu; Bourantas, Christos V; Iqbal, Javaid; Zhu, Hao; Cummins, Paul; Dong, Sheng-Jie; Mathur, Anthony; Zhang, Yao-Jun

    2018-02-22

    The study sought to compare angiographic and clinical outcomes of new-generation drug-eluting stents (DES) versus drug-coated balloon (DCB) in patients with coronary in-stent restenosis (ISR). Meta-analysis using data from randomised trial found by searches on PubMed, the Cochrane Library, ClinicalTrials.gov and websites of major cardiovascular congresses. Only randomised trials comparing DES with DCB were included. Patients with ISR in the included trials. New-generation DES versus DCB. The angiographic and clinical outcomes including cardiac death, all-cause death, myocardial infarction, target lesion revascularisation (TLR), target vessel revascularisation (TVR), major adverse cardiac events (MACE) and stent thrombosis were investigated. Five trials including 913 patients were eligible and included. Pooled analysis in angiographic results identified that new-generation DES were associated with higher acute luminal gain (-0.31 mm, 95% CI -0.42 to -0.20, PDES significantly reduced the risk of TLR (RR: 1.96, 95% CI 1.17 to 3.28, P=0.01) compared with DCB; however, there was no statistical differences for MACE (RR: 1.21, 95% CI 0.67 to 2.17, P=0.53), myocardial infarction (RR: 1.16, 95% CI 0.55 to 2.48, P=0.69) and cardiac death (RR: 1.80, 95% CI 0.60 to 5.39, P=0.29). Interventions with new-generation DES appear to be associated with significant reduction in per cent diameter stenosis and TLR at short-term follow-up, but had similar MACE, myocardial infarction and cardiac death for patients with coronary ISR compared with DCB. Appropriately powered studies with longer term follow-up are warranted to confirm these findings. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  10. Impact of Paclitaxel Dose on Tissue Pharmacokinetics and Vascular Healing: A Comparative Drug-Coated Balloon Study in the Familial Hypercholesterolemic Swine Model of Superficial Femoral In-Stent Restenosis.

    Science.gov (United States)

    Gongora, Carlos A; Shibuya, Masahiko; Wessler, Jeffrey D; McGregor, Jenn; Tellez, Armando; Cheng, Yanping; Conditt, Gerard B; Kaluza, Greg L; Granada, Juan F

    2015-07-01

    This study sought to compare the effect of paclitaxel-coated balloon (PCB) concentration on tissue levels and vascular healing using 3 different PCB technologies (In.Pact Pacific = 3 μg/mm(2), Lutonix = 2 μg/mm(2) and Ranger = 2 μg/mm(2)) in the experimental setting. The optimal therapeutic dose for PCB use has not been determined yet. Paclitaxel tissue levels were measured up to 60 days following PCB inflation (Ranger and In.Pact Pacific) in the superficial femoral artery of healthy swine (18 swine, 36 vessels). The familial hypercholesterolemic swine model of superficial femoral artery in-stent restenosis (6 swine, 24 vessels) was used in the efficacy study. Two weeks following bare-metal stent implantation, each in-stent restenosis site was randomly treated with a PCB or an uncoated control balloon (Sterling). Quantitative vascular analysis and histology evaluation was performed 28 days following PCB treatment. All PCB technologies displayed comparable paclitaxel tissue levels 4 h following balloon inflation. At 28 days, all PCB had achieved therapeutic tissue levels; however, the In.Pact PCB resulted in higher tissue concentrations than did the other PCB groups at all time points. Neointimal inhibition by histology was decreased in all PCB groups compared with the control group, with a greater decrease in the In.Pact group. However, the neointima was more mature and contained less peri-strut fibrin deposits in both 2-μg/mm(2) PCB groups. Compared with the clinically established PCB dose, lower-dose PCB technologies achieve lower long-term tissue levels but comparable degrees of neointimal inhibition and fewer fibrin deposits. The impact of these findings in restenosis reduction and clinical outcomes needs to be further investigated. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  11. A noise-optimized virtual monochromatic reconstruction algorithm improves stent visualization and diagnostic accuracy for detection of in-stent re-stenosis in lower extremity run-off CT angiography

    Energy Technology Data Exchange (ETDEWEB)

    Mangold, Stefanie [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Eberhard-Karls University Tuebingen, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany); De Cecco, Carlo N.; Yamada, Ricardo T.; Varga-Szemes, Akos; Stubenrauch, Andrew C.; Fuller, Stephen R. [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Schoepf, U.J. [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Medical University of South Carolina, Division of Cardiology, Department of Medicine, Charleston, SC (United States); Caruso, Damiano [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); University of Rome ' ' Sapienza' ' , Department of Radiological Sciences, Oncology and Pathology, Rome (Italy); Vogl, Thomas J.; Wichmann, Julian L. [Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt (Germany); Nikolaou, Konstantin [Eberhard-Karls University Tuebingen, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany); Todoran, Thomas M. [Medical University of South Carolina, Division of Cardiology, Department of Medicine, Charleston, SC (United States)

    2016-12-15

    To evaluate the impact of noise-optimized virtual monochromatic imaging (VMI+) on stent visualization and accuracy for in-stent re-stenosis at lower extremity dual-energy CT angiography (DE-CTA). We evaluated third-generation dual-source DE-CTA studies in 31 patients with prior stent placement. Images were reconstructed with linear blending (F{sub 0}.5) and VMI+ at 40-150 keV. In-stent luminal diameter was measured and contrast-to-noise ratio (CNR) calculated. Diagnostic confidence was determined using a five-point scale. In 21 patients with invasive catheter angiography, accuracy for significant re-stenosis (≥50 %) was assessed at F{sub 0}.5 and 80 keV-VMI+ chosen as the optimal energy level based on image-quality analysis. At CTA, 45 stents were present. DSA was available for 28 stents whereas 12 stents showed significant re-stenosis. CNR was significantly higher with ≤80 keV-VMI+ (17.9 ± 6.4-33.7 ± 12.3) compared to F{sub 0}.5 (16.9 ± 4.8; all p < 0.0463); luminal stent diameters were increased at ≥70 keV (5.41 ± 1.8-5.92 ± 1.7 vs. 5.27 ± 1.8, all p < 0.001) and diagnostic confidence was highest at 70-80 keV-VMI+ (4.90 ± 0.48-4.88 ± 0.63 vs. 4.60 ± 0.66, p = 0.001, 0.0042). Sensitivity, negative predictive value and accuracy for re-stenosis were higher with 80 keV-VMI+ (100, 100, 96.4 %) than F{sub 0}.5 (90.9, 94.1, 89.3 %). 80 keV-VMI+ improves image quality, diagnostic confidence and accuracy for stent evaluation at lower extremity DE-CTA. (orig.)

  12. Distinctive effects of CD34- and CD133-specific antibody-coated stents on re-endothelialization and in-stent restenosis at the early phase of vascular injury

    DEFF Research Database (Denmark)

    Wu, Xue; Yin, Tieying; Tian, Jie

    2015-01-01

    It is not clear what effects of CD34- and CD133-specific antibody-coated stents have on re-endothelialization and in-stent restenosis (ISR) at the early phase of vascular injury. This study aims at determining the capabilities of different coatings on stents (e.g. gelatin, anti-CD133 and anti-CD34......-coated stents, the time of cells adhesion was longer and earlier present in the anti-CD133 antibody-coated stents and anti-CD133 antibody-coated stents have superiority in re-endothelialization and inhibition of ISR. In conclusion, this study demonstrated that anti-CD133 antibody as a stent coating...... for capturing EPCs is better than anti-CD34 antibody in promoting endothelialization and reducing ISR....

  13. On the Possible Interaction Mechanism between Collateral Vessels and Restenosis

    NARCIS (Netherlands)

    Zun, P.S.; Hoekstra, A.G.

    2015-01-01

    Several clinical studies and their meta-analysis suggest that developed collateral vessels in the heart correlate to an increased risk of in-stent restenosis. The possible physiological interaction between the collateral development and in-stent restenosis is investigated in this study. Based on

  14. Evaluation of in-stent restenosis in the APPROACH trial (assessment on the prevention of progression by Rosiglitazone on atherosclerosis in diabetes patients with cardiovascular history)

    NARCIS (Netherlands)

    H.M. Garcia-Garcia (Hector); S.A. Garg (Scot); S. Brugaletta (Salvatore); G. Morocutti (Giorgio); R.E. Ratner (Robert); N.S. Kolatkar (Nikheel); B.G. Kravitz (Barbara); D.M. Miller (Diane); C. Huang (Chunmei); R.W. Nesto (Richard); P.W.J.C. Serruys (Patrick); R.P. Aftring (R.); N.S. Kolatkar (Nikheel); B.G. Kravitz (Barbara); J. Wolstenholme (Jane); J. Saarinen (Jari); R. Fowler (R.); J. Hoffman (Jonathan); D. Steele-Norwood (D.); R. Russell (Robert); S. Young (S.); Y.F. Chou; S. McMorn (Steve); C. Kirsch (Courtney); B. Louridas (Bonnie); T. Olivieria (Teresa); D. Mattioli (Debra); D. Miller (D.); C. Huang (Chunmei); C. Nguyen (C.); K. Jahnke (Kristoph); G.S. Mintz (Gary); J. Lachin (J.); M. Abrahamson (M.); P. Carson (P.); P. Jones

    2012-01-01

    textabstractTo determine (1) the medium-term effect of rosiglitazone and glipizide on intra-stent neointima hyperplasia, (2) restenosis pattern as assessed by intravascular ultrasound (IVUS) and quantitative coronary angiography (QCA) in patients with T2DM and coronary artery disease. A total of 462

  15. Impact of stent diameter and length on in-stent restenosis after DES vs BMS implantation in patients needing large coronary stents-A clinical and health-economic evaluation

    DEFF Research Database (Denmark)

    Zbinden, Rainer; von Felten, Stefanie; Wein, Bastian

    2017-01-01

    AIMS: The British National Institute of Clinical Excellence (NICE) guidelines recommend to use drug-eluting stents (DES) instead of bare-metal stents (BMS) only in lesions >15 mm in length or in vessels 3 mm in diameter. We analyzed the impact of stent length and stent diameter on in......-stent restenosis (ISR) in the BASKET-PROVE study population and evaluated the cost-effectiveness of DES compared to BMS. METHODS/RESULTS: The BASKET-PROVE trial compared DES vs BMS in large coronary arteries (≥3 mm). We calculated incremental cost-effectiveness ratios (ICERs) and cost-effectiveness acceptability...... of 10 000 CHF per TLR avoided, DES had a high probability of being cost-effective. CONCLUSION: In the BASKET-PROVE study population, the strongest predictor of ISR is the use of a BMS, even in patients in need of stents ≥3.0 mm and ≤15 mm lesion length and DES were cost-effective. This should prompt...

  16. Short- versus long-term duration of dual antiplatelet therapy in patients treated for in-stent restenosis: a PRODIGY trial substudy (Prolonging Dual Antiplatelet Treatment After Grading Stent-Induced Intimal Hyperplasia).

    Science.gov (United States)

    Campo, Gianluca; Tebaldi, Matteo; Vranckx, Pascal; Biscaglia, Simone; Tumscitz, Carlo; Ferrari, Roberto; Valgimigli, Marco

    2014-02-18

    This study sought to investigate the clinical outcome of patients treated with percutaneous coronary intervention (PCI) for in-stent restenosis (ISR) randomized to short (6 months) versus long (24 months) dual antiplatelet therapy (DAPT) regimen. It is still unclear if patients treated for ISR may benefit from a long DAPT regimen. For the present purpose, we selected 224 patients undergoing the PCI procedure for ISR enrolled in the PRODIGY (Prolonging Dual Antiplatelet Treatment After Grading Stent-Induced Intimal Hyperplasia) trial and randomized to short (6 months) versus long (24 months) DAPT regimen. The primary objective was the cumulative incidence of death, nonfatal myocardial infarction (MI), or cerebrovascular accident at 24 months. Safety endpoints were moderate and major bleeding complications. Overall, 114 patients were allocated to short DAPT regimen, whereas 110 patients were allocated to long DAPT regimen. Twenty-seven patients reached the primary endpoint (19 in short DAPT regimen vs. 8 in long DAPT regimen; p = 0.02). The cumulative incidence of the primary endpoint at 24 months was 16.7% in the short DAPT regimen group compared with 7.3% in the long DAPT regimen group (p = 0.034). This is principally due to a lower occurrence of death and MI in the long DAPT regimen group as compared to the short DAPT regimen group (6.5% vs. 15.5%; p = 0.03). There was no difference in the occurrence of bleeding complications between long and short DAPT regimen. Our study offers preliminary evidence that patients receiving a new PCI procedure for ISR may benefit from long-term administration of aspirin plus clopidogrel. (Synergy Between Stent and Drugs to Avoid Ischemic Recurrences After Percutaneous Coronary Intervention [PRODIGY]; NCT00611286). Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  17. Braquiterapia intracoronariana. Tratamento da reestenose intra-stent com o sistema Beta-Cath: experiência inicial na América Latina Intracoronary brachytherapy. Treatment of in-stent restenosis with the Beta-Cath system: initial experience in Latin America

    Directory of Open Access Journals (Sweden)

    Juan Simon Muñoz

    2004-07-01

    . METHODS: This study assessed 30 patients with ISR in native coronary arteries who underwent balloon catheter angioplasty followed by intracoronary beta radiation with the Beta-Cath systemTM (90Sr/Y. RESULTS: The study comprised complex, extensive (18.66±4.15 mm restenotic lesions, 77% of which were of the diffuse-proliferative type. Brachytherapy was successful in 100% of the cases. The mean radiation dose used was 20.7±2.3 Gy, released for a mean period of 3.8±2.1 minutes. On late follow-up, the in-stent minimum luminal diameter (MLD slightly decreased (from 1.98±0.30 mm to 1.84±0.39 mm at 6 months; P=0.13, with a late loss of 0.14±0.18 mm. The intrasegmentary MLD was significantly smaller than the in-stent diameter (1.55±0.40 mm vs 1.84±0.39 mm; P=0.008, and was associated with a more significant late loss (0.40±0.29 mm vs 0.14±0.18 mm; P=0.0001. On ICUS, a mild increase of 6.8±14.3 mm³ in the neointimal tissue was observed at 6 months (P=0.19, and the percentage of volumetric obstruction increased by 4.7±7.5%. Binary restenosis and revascularization of the target vessel recurred in 17% of the cases; late occlusion associated with myocardial infarction occurred in 1 case (3%. Event-free survival was 80%. CONCLUSION: The management of in-stent restenosis with intracoronary beta radiation proved to be a safe and effective procedure, with a high rate of immediate success, representing a therapeutic option for inhibiting neointimal hyperplasia.

  18. Comparison among drug-eluting balloon, drug-eluting stent, and plain balloon angioplasty for the treatment of in-stent restenosis: a network meta-analysis of 11 randomized, controlled trials.

    Science.gov (United States)

    Lee, Joo Myung; Park, Jonghanne; Kang, Jeehoon; Jeon, Ki-Hyun; Jung, Ji-Hyun; Lee, Sang Eun; Han, Jung-Kyu; Kim, Hack-Lyoung; Yang, Han-Mo; Park, Kyung Woo; Kang, Hyun-Jae; Koo, Bon-Kwon; Kim, Hyo-Soo

    2015-03-01

    A Bayesian network meta-analysis was performed comparing the efficacy and safety of drug-eluting balloons (DEB), drug-eluting stents (DES), or plain old balloon angioplasty (POBA) for treatment of in-stent restenosis (ISR). Optimal treatment options for ISR have not been well established. Randomized, controlled trials comparing DEB, DES, and POBA for the treatment of ISR after percutaneous coronary intervention with bare metal stent or DES were included. The primary outcome was target lesion revascularization (TLR). The pairwise posterior median odds ratio (OR) with 95% credible interval (CrI) was the effect measure. This analysis included 2,059 patients from 11 RCTs. The risk of TLR was markedly lower in patients treated with DEB (OR: 0.22, 95% CrI: 0.10 to 0.42) or DES (OR: 0.24, 95% CrI: 0.11 to 0.47) than in those treated with POBA in a random-effects model. In a comparison of DEB and DES, the risk of TLR (OR: 0.92, 95% CrI: 0.43 to 1.90) was similar. The risk of MI or all-cause mortality was lowest in the DEB group compared with the DES and POBA groups, which did not meet statistical significance. The risk of major adverse cardiac events, which was mainly driven by TLR, was also significantly lower in the DEB or and DES group (OR: 0.28, 95% CrI: 0.14 to 0.53) than in the POBA group, but it was similar between the DEB and DES groups (OR: 0.84, 95% CrI: 0.45 to 1.50). The probability of being ranked as the best treatment was 59.9% (DEB), 40.1% (DES), and 0.1% (POBA) in terms of TLR, whereas it was 63.0% (DEB), 35.3% (POBA), and 1.7% (DES) in terms of MI. Local drug delivery by DEB or DES for ISR lesions was markedly better than POBA in preventing TLR, but not for MI or mortality. Among the 2 different strategies of drug delivery for ISR lesions, treatment with DEB showed a trend of less development of MI than did treatment with DES. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  19. Intravascular ultrasound assessment of minimumlumen area and intimal hyperplasia in in-stent restenosis after drug-eluting or bare-metal stent implantation. The Nordic Intravascular Ultrasound Study (NIVUS)

    DEFF Research Database (Denmark)

    Jensen, Lisette Okkels; Vikman, Saila; Antonsen, Lisbeth

    2017-01-01

    Introduction: Drug-eluting stents (DES) reduce the risk of restenosis after percutaneous coronary intervention. The aim of the study was to evaluate, by intravascular ultrasound (IVUS), the minimum lumen area site in the stented segment and the distribution of intimal hyperplasia in patients...

  20. Predictors of 32P β brachytherapy failure in patients with high-risk in-s tent restenosis

    International Nuclear Information System (INIS)

    Ortolani, Paolo; Marzocchi, Antonio; Aquilina, Matteo; Gaiba, William; Bunkheila, Feisal; Neri, Stefano; Lombardo, Enzo; Marrozzini, Cinzia; Pini, Stefania; Taglieri, Nevio; Sbarzaglia, Paolo; Reggiani, Maria Letizia Bacchi; Barbieri, Enza; Branzi, Angelo

    2004-01-01

    Background: The effectiveness of coronary radiation therapy for the treatment of in-stent restenosis (ISR) has been established in several randomized clinical trials. The efficacy of this treatment in the general population is less well established. Methods and materials: We report our experience in 118 consecutive patients with nonselected high-risk ISR who had undergone successful percutaneous coronary intervention and brachytherapy with 32 P β-irradiation and who were prospectively enrolled in a quantitative angiographic and clinical follow-up protocol at 7 months after the index procedure. The aim of this study was to investigate the independent predictor of angiographic restenosis after 32 P brachytherapy treatment. Results: Of the patients, 28.8% were diabetics. The mean lesion and mean radiated lengths were, respectively, 30.1 ± 17.2 and 43.8 ± 16.9 mm. The ISR pattern was diffuse in 96% of the treated lesions; in particular, 22.1% presented an occlusive pattern and 37.1% a proliferative pattern. At follow-up angiographic, restenosis and major adverse cardiac events (MACE) rates were, respectively, 20.8% and 29.6%. The univariate predictors of angiographic restenosis were procedural geographic miss, pattern IV ISR, manual pullback maneuver of the radiation source, preprocedural lesion percentage stenosis and preprocedural lesion MLD. At logistic regression analysis, only geographic miss and pattern IV ISR were independent predictors of post intracoronary radiation therapy (IRT) angiographic restenosis. Conclusion: These data indicate that 7-month angiographic restenosis after 32 P IRT in complex patients with ISR is not a frequent event and is predicted mainly by an occlusive lesion at baseline and by procedural geographical miss

  1. Coronary stent restenosis and the association with allergy to metal content of 316L stainless steel.

    Science.gov (United States)

    Slodownik, D; Danenberg, C; Merkin, D; Swaid, F; Moshe, S; Ingber, A; Lotan, H; Durst, R

    Most intra-coronary stents in use are made of 316 L stainless steel, which contains nickel, chromate and molybdenum. Whether inflammatory and allergic reactions to metals contribute to in-stent restenosis is still a matter of debate. The aim of this study was to ascertain the relationship between metal allergy and the occurrence of in-stent restenosis. Ninety-nine adult patients who underwent two cardiac catheterisations, up to two years apart, were included in the study. Seventy patients had patent stents at the second angiogram (patent stent group) and 29 were found to have in-stent restenosis (restenosis group). All patients underwent patch testing with the relevant metals and the 316L stainless steel plate. Twenty-eight (28.3%) patients were found to have an allergy to at least one metal. There was no significant difference in the prevalence of metal allergy between the patent stent group and the restenosis group (28.6 and 27.6%, respectively; p = 0.921). Our data do not support the theory that contact allergy plays a role in the pathogenesis of in-stent restenosis.

  2. Restenosis after stenting in symptomatic vertebral arterial orifice disease and considerations for better outcome

    Science.gov (United States)

    Chang, Jun Young; Park, Hyun; Kwon, Oki

    2017-01-01

    We have performed stenting in 11 patients with symptomatic vertebral arterial orifice stenosis refractory to medical treatment or impairment in anterior circulation. Three of the 11 patients experienced asymptomatic severe in-stent restenosis or occlusion. Bare metal stents were used in those three patients, two of whom received revascularization therapy. Development of sufficient cervical collateral channels reconstituting the distal vertebral artery was the common feature in patients with asymptomatic in-stent restenosis. In selecting appropriate stents, consideration of mechanical strength and drug-eluting properties of a stent according to characteristics of the target vessel is important to reduce the risk of in-stent restenosis. Any decision to perform revascularization should be based on the presence of abundant cervical collaterals as well as clinical symptoms of vertebrobasilar ischemia. PMID:28304206

  3. Restenosis after coronary angioplasty.

    Science.gov (United States)

    Anderson, H V; Vignale, S J; Benedict, C R; Willerson, J T

    1993-09-01

    Coronary angioplasty is used to treat coronary atherosclerotic disease in many patients. One problem with coronary angioplasty is the phenomenon of restenosis. Restenosis appears to be a universal response to arterial wall injury. The biological events that underlie restenosis are characterized by: platelet adhesion and aggregation at sites of damaged endothelium, and within dissections into the medial layers, release of platelet derived growth-promoting substances, inflammation of the injured medial zone, transformation, migration, and proliferation of smooth muscle cells of the media following their activation by growth-promoting substances, secretion of copious amounts of extracellular matrix material, and finally, termination of the growth process following regrowth of endothelium over the damaged area. More than a decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesion and multivessel procedures, higher post-angioplasty residual stenosis, proximal vessel location, location in the left anterior descending coronary artery, location in a vein graft, long lesions, and total occlusions. However, for the purposes of individual patient care, clinical correlates are not particularly helpful. No group of variables has predicted complete freedom from restenosis, and conversely no group of variables has reliably indicated its presence. All patients undergoing angioplasty will require some form of follow-up evaluation. Symptom status by itself has not been found to be useful for predicting restenosis. However, when symptom status is combined with exercise thallium-201 scintigraphy, performed 4-6 months after angioplasty, it is less than ideal, but has a negative predictive value of over 90%. This means that over 90% of patients who are asymptomatic and have no

  4. Matrix metalloproteinase 9 level as an indicator for restenosis following cervical and intracranial angioplasty and stenting

    Directory of Open Access Journals (Sweden)

    Jun-peng Liu

    2015-01-01

    Full Text Available Cervical and intracranial angioplasty and stenting is an effective and safe method of reducing the risk of ischemic stroke, but it may be affected by in-stent restenosis. The present study investigated serum level of matrix metalloproteinase 9 as a predictor of restenosis after 40 patients underwent cervical and/or intracranial angioplasty and stenting. Results showed that restenosis occurred in 30% (3/10 of patients when the serum level of matrix metalloproteinase 9 at 3 days after surgery was 2.5 times higher than preoperative level. No restenosis occurred when the serum level of matrix metalloproteinase 9 at 3 days after surgery was not 2.5 times higher than preoperative level. Restenosis occurred in 12% (2/17 of patients when the serum level of matrix metalloproteinase 9 was higher than preoperative level for more than 30 days after surgery, but only occurred in 4% (1/23 of patients when the serum level of matrix metalloproteinase 9 was higher than preoperative level for less than 30 days after surgery. However, the differences observed were not statistically significant (P > 0.05. Experimental findings indicate that when the serum level of matrix metalloproteinase 9 is 2.5 times higher than preoperative level at 3 days after cervical and intracranial angioplasty and stenting, it may serve as a predictor of in-stent restenosis.

  5. Radioactive stents delay but do not prevent in-stent neointimal hyperplasia

    NARCIS (Netherlands)

    I.P. Kay (Ian Patrick); A.J. Wardeh (Alexander); K. Kozuma (Ken); A.H.M. Knook (Marco); A. Thury (Attila); P.W.J.C. Serruys (Patrick); D.P. Foley (David); P.C. Levendag (Peter); W.J. van der Giessen (Wim); G. Sianos (Georgios)

    2001-01-01

    textabstractBACKGROUND: Restenosis after conventional stenting is almost exclusively caused by neointimal hyperplasia. Beta-particle-emitting radioactive stents decrease in-stent neointimal hyperplasia at 6-month follow-up. The purpose of this study was to evaluate the 1-year outcome of (32)P

  6. Comparison of plain balloon and cutting balloon angioplasty for the treatment of restenosis with drug-eluting stents vs bare metal stents.

    Science.gov (United States)

    Park, Seung-Jung; Kim, Kyung-Hee; Oh, Il-Young; Shin, Dong-Ho; Park, Kyung-Il; Seo, Myung-Ki; Chung, Jin-Wook; Park, Kyung Woo; Lee, Hae-Young; Kang, Hyun-Jae; Koo, Bon-Kwon; Youn, Tae-Jin; Kim, Hyo-Soo

    2010-09-01

    The efficacy of cutting or plain balloon angioplasty (CBA or PBA) has not been analyzed for the treatment of drug-eluting stent (DES) restenosis vs bare metal stent (BMS) restenosis. The 252 in-stent restenosis (ISR) lesions in 224 consecutive patients treated by CBA (n=167) or PBA (n=85) between July 2002 and December 2007 were analyzed. At 6-month angiographic and 12-month clinical follow-up, CBA and PBA showed similar efficacies: repeat-ISR (37.0% vs 37.8%, P=0.90), late loss (0.62+/-0.60 vs 0.61+/-0.47 mm, P=0.92), and target lesion revascularization (18.3% vs 22.4%, P=0.50). This comparable efficacy was maintained for treatment in the DES-ISR and BMS-ISR subgroups. However, target lesion-related myocardial infarction (n=9) occurred more frequently in the CBA than in the PBA arm (6.2% vs 0%, P=0.03), most of which developed early after ISR treatment (n=7; 54+/-26 days). Independent predictors of repeat-ISR were diffuse ISR and smaller pretreatment minimal lumen diameter, both of which might imply heavier plaque burden in the ISR group. Plain or cutting balloon angioplasty for ISR seems to be comparable, as the angiographic or clinical endpoints were not affected by initial stent type but by parameters related to the plaque burden of the ISR lesion. However, CBA might be associated with higher risk of myocardial infarction than PBA, suggesting more attention to dual-antiplatelet therapy after its use for ISR.

  7. Coated stents to prevent restenosis in coronary heart disease

    Directory of Open Access Journals (Sweden)

    Hagen, Anja

    2005-11-01

    Full Text Available Background: In-stent-restenosis (ISR is considered to be an essential limiting factor of stenting in coronary heart disease (CHD. The development of coated stents has raised expectations on substantial lowering restenosis after stenting with decreasing the rate of restenosis and a reduction in the rate of clinical events. Objectives: The present analysis addresses the questions on medical effectiveness and cost-effectiveness of the use of various coated stent types in CHD. Methods: The literature was searched in December 2004 in the most relevant medical and economic databases. The medical evaluation was conducted on the basis of published RCT. The data from the studies regarding various angiographic, sonographic and clinical endpoints were checked for methodical quality and summarised in meta-analyses. Within the scope of economic evaluation the primary studies were analysed and modelling was performed, applying clinical effect estimates from the meta-analyses of the medical evaluation and current estimates of German costs. Results: Medical evaluation: Ten different stenttypes were used in the included 26 RCT. The results for heparin, silicon-carbide, carbon and PTFE coated stenttypes could not reveal any significant differences between the medical effectiveness of coated and uncoated stents. The application of sirolimus, paclitaxel, everolimus and 7-hexanoyltaxol eluting stents showed a significant lower restenosis at 6-9 months with decrease in the rate of restenosis for polymer-based sirolimus, paclitaxel and 7-hexanoyltaxol eluting stents. In contrast, the use of gold-coated and actinomycin-D eluting stents was associated with a significantly higher restenosis. The polymer-based sirolimus and paclitaxel eluting stents also showed a significant and considerable reduction in the rate of repeated percutaneous revascularisations at 6-12 months (3.5% vs. 19.7%; p<0.0001, RR=0.19 [95%CI: 0.11; 0.33] and 3.5% vs. 12.2%; p<0.0001, RR=0.30 [95%CI: 0

  8. Restenosis: A Challenge to Angioplasty

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 4. Restenosis: A Challenge to Angioplasty. M S S Murthy. General Article Volume 6 Issue 4 April 2001 pp 52-61. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/006/04/0052-0061. Author Affiliations.

  9. Novel A20-gene-eluting stent inhibits carotid artery restenosis in a porcine model

    Directory of Open Access Journals (Sweden)

    Zhou ZH

    2016-08-01

    Full Text Available Zhen-hua Zhou,1 Jing Peng,1 Zhao-you Meng,1 Lin Chen,1 Jia-Lu Huang,1 He-qing Huang,1 Li Li,2 Wen Zeng,2 Yong Wei,2 Chu-Hong Zhu,2 Kang-Ning Chen1 1Department of Neurology, Cerebrovascular Disease Research Institute, Southwest Hospital, 2Department of Anatomy, Key Laboratory for Biomechanics of Chongqing, Third Military Medical University, Chongqing, People’s Republic of China Background: Carotid artery stenosis is a major risk factor for ischemic stroke. Although carotid angioplasty and stenting using an embolic protection device has been introduced as a less invasive carotid revascularization approach, in-stent restenosis limits its long-term efficacy and safety. The objective of this study was to test the anti-restenosis effects of local stent-mediated delivery of the A20 gene in a porcine carotid artery model.Materials and methods: The pCDNA3.1EHA20 was firmly attached onto stents that had been collagen coated and treated with N-succinimidyl-3-(2-pyridyldithiolpropionate solution and anti-DNA immunoglobulin fixation. Anti-restenosis effects of modified vs control (the bare-metal stent and pCDNA3.1 void vector stents were assessed by Western blot and scanning electron microscopy, as well as by morphological and inflammatory reaction analyses.Results: Stent-delivered A20 gene was locally expressed in porcine carotids in association with significantly greater extent of re-endothelialization at day 14 and of neointimal hyperplasia inhibition at 3 months than stenting without A20 gene expression.Conclusion: The A20-gene-eluting stent inhibits neointimal hyperplasia while promoting re-endothelialization and therefore constitutes a novel potential alternative to prevent restenosis while minimizing complications. Keywords: restenosis, A20, gene therapy, stent, endothelialization

  10. An analysis of three dimensional diffusion in a representative arterial wall mass transport model.

    Science.gov (United States)

    Denny, William J; O'Connell, Barry M; Milroy, John; Walsh, Michael T

    2013-05-01

    The development and use of drug eluting stents has brought about significant improvements in reducing in-stent restenosis, however, their long term presence in the artery is still under examination due to restenosis reoccurring. Current studies focus mainly on stent design, coatings and deployment techniques but few studies address the issue of the physics of three dimensional mass transport in the artery wall. There is a dearth of adequate validated numerical mass transport models that simulate the physics of diffusion dominated drug transport in the artery wall whilst under compression. A novel experimental setup used in a previous study was adapted and an expansion of that research was carried out to validate the physics of three dimensional diffusive mass transport into a compressed porous media. This study developed a more sensitive method for measuring the concentration of the species of interest. It revalidated mass transport in the radial direction and presented results which highlight the need for an evaluation of the governing equation for transient diffusive mass transport in a porous media, in its current form, to be carried out.

  11. Carotid stenting using tapered and nontapered stents: associated neurological complications and restenosis rates.

    Science.gov (United States)

    Brown, Katherine E; Usman, Asad; Kibbe, Melina R; Morasch, Mark D; Matsumura, Jon S; Pearce, William H; Amaranto, Daniel J; Eskandari, Mark K

    2009-01-01

    Self-expanding stent design systems for carotid artery stenting (CAS) have morphed from nontapered (NTS) to tapered (TS); however, the impact of this change is unknown. We reviewed the outcomes of CAS with these two broad categories of stents in a single-center retrospective review of 308 CAS procedures from May 2001 to July 2007. Nitinol self-expanding TS or NTS coupled with cerebral embolic protection devices were used to treat extracranial carotid occlusive disease. Data analysis included demographics, procedural records, duplex exams, and conventional arteriography. Mean follow-up was 18 months (range 1-69). Restenosis was defined as >or=80% in-stent carotid artery stenosis by angiography. The mean age of the entire cohort was 71.3 years (75% men, 25% women). Of the 308 cases, 233 were de novo lesions and 75 had a prior ipsilateral carotid endarterectomy (n = 44) or external beam radiation exposure (n = 31). Preprocedure neurological symptoms were present in 30% of patients. TS were used in 156 procedures and NTS in 152 procedures. The 30-day ipsilateral stroke and death rates were 1.3% and 0.3%, respectively. An additional three (1.0%) posterior circulation strokes occurred. There was no statistically significant difference in the 30-day total stroke rates between TS (3.2%, n = 5) and NTS (1.3%, n = 2) (p = 0.5). At midterm follow-up, restenosis or asymptomatic occlusion was detected in eight cases (2.6%). All occurred in arteries treated with NTS, and this was statistically different when compared to arteries treated with TS (p = 0.03). Furthermore, a post-hoc subgroup analysis revealed significant correlation (chi(2) = 0.02) for restenosis in "hostile necks" when separated by TS vs. NTS. Early CAS outcomes between TS and NTS are comparable. In contrast, self-expanding nitinol TS may have a lower incidence of significant restenosis or asymptomatic occlusion when compared to NTS.

  12. The SABRE Trial (Sirolimus Angioplasty Balloon for Coronary In-Stent Restenosis)

    DEFF Research Database (Denmark)

    Verheye, Stefan; Vrolix, Mathias; Kumsars, Indulis

    2017-01-01

    centers, 50 ISR patients were treated with the Virtue balloon. Angiographic measurements at 6 months are reported, along with 12-month clinical follow-up. RESULTS Procedural success in the intention-to-treat population was 100 The primary safety endpoint was target lesion failure (TLF) (cardiac death...... and 14.3% MACE and for the per-protocol population were 2.8% TLF and 2.8% MACE. CONCLUSIONS This first-in-human study showed excellent procedural success for the Virtue sirolimus-eluting angioplasty balloon, 6-month LLL rates in line with current stent-free ISR treatment options, and clinical outcomes...

  13. Diagnostic efficacy for coronary in-stent patency with parameters defined on Hounsfield CT value-spatial profile curves

    International Nuclear Information System (INIS)

    Yamazaki, Tadashi; Suzuki, Jun-ichi; Shimamoto, Ryoichi; Tsuji, Taeko; Ohmoto-Sekine, Yuki; Morita, Toshihiro; Yamashita, Hiroshi; Honye, Junko; Nagai, Ryozo; Komatsu, Shuhei; Akahane, Masaaki; Ohtomo, Kuni

    2008-01-01

    Purpose: Hounsfield CT values across coronary CT angiograms constitute CT value-spatial profile curves. These CT profile curves are independent of window settings, and therefore, parameters derived from the curves can be used for objective anatomic analyses. Applicability of parameters derived from the curves to quantification of coronary in-stent patency has not yet been evaluated. Methods: Twenty-five CT value-spatial profile curves were delineated from 10 consecutive coronary stents to test correlation between the curve derived parameter (i.e., the minimum extreme value normalized by dividing by the maximum value of the curves obtained at neighboring outside of stents) and three intravascular ultrasound (IVUS) parameters. Results: Correlation coefficients between normalized minimum extreme value of CT value-spatial profile curves and three IVUS parameters (such as patent cross-sectional in-stent area, the percentage of patent cross-sectional in-stent area, and coronary artery intra-stent diameter) were 0.65 (p < 0.01), 0.44 (p < 0.05) and 0.51 (p < 0.05), respectively. Conclusions: CT parameters defined on Hounsfield CT value-spatial profile curves correlated significantly with IVUS parameters for quantitative coronary in-stent patency. A new approach with CT coronary angiography is therefore indicated for the noninvasive assessment of in-stent re-stenosis

  14. Endovascular brachytherapy to prevent restenosis after angioplasty; Endovaskulaere Brachytherapie in der Restenoseprophylaxe nach Angioplastie und Stentimplantation: Eine Uebersicht

    Energy Technology Data Exchange (ETDEWEB)

    Wohlgemuth, W.A.; Bohndorf, K. [Klinikum Augsburg (Germany). Klinik fuer Diagnostische Radiologie und Neuroradiologie

    2003-02-01

    Endovascular radiotherapy is the first effective prophylaxis of restenosis after percutaneous transluminal angioplasty (PTA) and stenting. The FDA recently approved two devices for the delivery of intracoronary radiation following coronary artery stenting. Published multicenter, double-blind, randomized trials of intracoronary radiation therapy report good results for preventing in-stent restenosis, while the data for the peripheral circulation are still inconclusive. Beta-emitters are easier applicable and probably also safer, whereas gamma-emitters have been more extensively evaluated clinically so far. Primary indication for endovascular brachytherapy are patients at high risk for restenosis, such as previous restenoses, in-stent hyperplasia, long stented segment, long PTA lesion, narrow residual vascular lumen and diabetes. Data from coronary circulation suggest a safety margin of at least 4 to 10 mm at both ends of the angioplastic segment to avoid edge restenosis. To prevent late thrombosis of the treated coronary segment, antiplatelet therapy with clopidogrel and aspirin are recommended for at least 6 months after PTA and for 12 months after a newly implanted stent. An established medication regimen after radiotherapy of peripheral arteries is still lacking. (orig.) [German] Die endovaskulaere Radiotherapie stellt das erste erfolgreiche Therapiekonzept in der Restenoseprophylaxe nach PTA und Stentimplantation dar. Am 3.11.2000 hat die amerikanische Food and Drug Administration erstmalig zwei Brachytherapiegeraete zur Restenoseprophylaxe nach Koronararterien-Stenting zugelassen. Grosse multizentrische, kontrollierte Studien wurden fuer das koronare Stromgebiet mit positiven Ergebnissen publiziert, die Datenlage im peripheren Stromgebiet ist noch ungenuegend. Beta-Strahler bieten Vorteile in der Anwendung, moeglicherweise auch in der Sicherheit, Gamma-Strahler dagegen sind besser klinisch evaluiert. Die primaere Indikation zur endovaskulaeren Brachytherapie

  15. Local drug delivery to prevent restenosis.

    Science.gov (United States)

    Seedial, Stephen M; Ghosh, Soumojit; Saunders, R Scott; Suwanabol, Pasithorn A; Shi, Xudong; Liu, Bo; Kent, K Craig

    2013-05-01

    Despite significant advances in vascular biology, bioengineering, and pharmacology, restenosis remains a limitation to the overall efficacy of vascular reconstructions, both percutaneous and open. Although the pathophysiology of intimal hyperplasia is complex, a number of drugs and molecular tools have been identified that can prevent restenosis. Moreover, the focal nature of this process lends itself to treatment with local drug administration. This article provides a broad overview of current and future techniques for local drug delivery that have been developed to prevent restenosis after vascular interventions. A systematic electronic literature search using PubMed was performed for all accessible published articles through September 2012. In an effort to remain current, additional searches were performed for abstracts presented at relevant societal meetings, filed patents, clinical trials, and funded National Institutes of Health awards. The efficacy of local drug delivery has been demonstrated in the coronary circulation with the current clinical use of drug-eluting stents. Until recently, however, drug-eluting stents were not found to be efficacious in the peripheral circulation. Further pursuit of intraluminal devices has led to the development of balloon-based technologies, with a recent surge in trials involving drug-eluting balloons. Early data appear encouraging, particularly for treatment of superficial femoral artery lesions, and several devices have recently received the Conformité Européene mark in Europe. Investigators have also explored the periadventitial application of biomaterials containing antirestenotic drugs, an approach that could be particularly useful for surgical bypass or endarterectomy. In the past, systemic drug delivery has been unsuccessful; however, there has been recent exploration of intravenous delivery of drugs designed specifically to target injured or reconstructed arteries. Our review revealed a multitude of additional

  16. Ultrasound thrombolysis in stent thrombosis.

    Science.gov (United States)

    Rassin, T; Desmet, W; Piessens, J; Rosenschein, U

    2000-11-01

    Recent refinement in stent implantation technique and peri-procedural pharmacological treatment has lowered the incidence of stent thrombosis significantly. Still, all stent thromboses are associated with major adverse events. In previous studies it has been suggested that intravascular ultrasound fibrinolysis is safe and effective. In this report, ultrasound successfully reperfused thrombotically occluded stents. These observations suggest that ultrasound may dissolve occlusive platelet-rich thrombus effectively and safely. Cathet. Cardiovasc. Intervent. 51:332-334, 2000. Copyright 2000 Wiley-Liss, Inc.

  17. Patterns of restenosis for the SFA: The second step on a long journey.

    Science.gov (United States)

    Ansel, Gary M

    2017-10-01

    Restenosis patterns required better definitions Defining restenosis patterns may help compare technologies better Further research with consistent restenosis pattern definition will help us define the most value-added treatments. © 2017 Wiley Periodicals, Inc.

  18. Do pre-procedural laboratory parameters predict drug-eluting stent restenosis?

    Science.gov (United States)

    Tanındı, Aslı; Ekici, Berkay; Töre, Hasan Fehmi

    2015-07-01

    Drug-eluting stents (DES) have considerably reduced the rates of in-stent restenosis (ISR). Several studies reported pre-procedural C-reactive protein (CRP), neutrophil to lymphocyte (N/L) ratio, red cell distribution width (RDW), serum uric acid (UA), and mean platelet volume (MPV) as independent predictors of ISR using bare metal stents. This study investigates whether any laboratory parameter obtained before the coronary stenting procedure is associated with ISR using DES in stable coronary artery disease. Three hundred fifteen stents were retrospectively analysed in 285 patients who had undergone coronary stenting and a control coronary angiography within one year of stenting, between January 2012 and April 2014. Pre-procedural complete blood count, biochemistry, and CRP were recorded. Off-line quantitative coronary angiography analysis was performed. Overall restenosis rate was 10.2%. When the stents were analysed with respect to the presence of ISR, the number of diabetics and smokers was higher in the ISR group. CRP levels were significantly higher in the ISR group, but there were no differences in N/L, monocytes, eosinophils, RDW, MPV, UA, and total bilirubin levels. In the univariate regression analysis, DM, CRP, stent length, stent diameter, pre-procedural diameter stenosis, pre-procedural minimal lumen diameter (MLD), post-procedural residual diameter stenosis, post-procedural reference vessel diameter, and post-procedural MLD were predictors of ISR. However, multivariate regression analysis identified only DM and post-procedural residual stenosis as independent predictors of ISR. Pre-procedural blood parameters do not independently predict ISR in DES, which is mainly determined by the presence of diabetes and post-procedural residual stenosis.

  19. External Beam Irradiation and Restenosis Following Femoral Stenting: Long-Term Results of a Prospective Randomized Study

    International Nuclear Information System (INIS)

    Zampakis, Petros; Karnabatidis, Dimitrios; Kalogeropoulou, Christina; Kardamakis, Dimitrios M.; Katsanos, Konstantinos; Skouras, Theodoros; Siablis, Dimitrios

    2007-01-01

    Purpose. To assess the long-term outcome of external beam irradiation (EBI) for the prevention of restenosis due to neointimal hyperplasia, following percutaneous transluminal angioplasty (PTA) and stenting of the superficial femoral artery. Methods. Sixty consecutive patients with peripheral arterial disease, who were treated with 'bail-out' stent implantation in the superficial femoral artery due to suboptimal PTA, were included in this study. Patients were randomly allocated into two groups, receiving either external beam irradiation (6 MV photons, total dose 24 Gy in a hypofractionated schedule) plus antiplatelet therapy (EBI group) or antiplatelet therapy alone (control group). Results. No procedure-related complications occurred, and all patients of the EBI group received the full dose of 24 Gy. During the long-term follow-up, an overall statistically significant difference was demonstrated in favor of the EBI group patients, regarding both the in-stent (log-rank test, p = 0.0072) and the in-segment binary restenosis (log-rank test, p = 0.0103). The primary patency rates were also significantly better in the EBI group at specific time-points, such as in the first (74.2% vs 46.5%, p = 0.019), second (62.5% vs 33.8%, p = 0.020), and third (54.6% vs 29.0%, p = 0.039) year, respectively. Moreover, the overall clinically driven reintervention rate was significantly lower among patients of the irradiated group (log-rank test, p = 0.038). Conclusion. Our long-term follow-up analysis revealed that EBI following femoral artery PTA and stenting significantly reduces restenosis and reintervention rates, while improving primary patency

  20. Redefining the boundaries of drug-eluting stent utilization: from in-stent restenosis to acute myocardial infarction

    NARCIS (Netherlands)

    F. Saia (Francesco)

    2004-01-01

    textabstractPercutaneous Coronary Interventions Percutaneous coronary angioplasty was first introduced by Andreas Gruentzig in 1977 as a non surgical method for coronary artery revascularization. Although initially restricted to stable patients with single, discrete, concentric, noncalcified

  1. Evaluating the cost of therapy for restenosis: considerations for brachytherapy.

    Science.gov (United States)

    Weintraub, W S

    1996-11-01

    Costs have become increasingly important in medicine in recent years as demand for services has outstripped readily available resources. Clinical microeconomics offers an approach to understanding cost and outcomes in an environment of economic scarcity. In this article the types of costs and methods for determining cost are presented. In addition, methods for assessing outcome and outcome in relation to cost are developed. Restenosis after coronary angioplasty is a prime example of a clinical problem requiring economic evaluation. This is because it results in little serious morbidity except for recurrent chest pain, but it has serious economic consequences which occur some time after the original angioplasty. This makes the economic assessment of restenosis complicated. The application of health care microeconomic principles to brachytherapy for restenosis in the coronary arteries is presented.

  2. Evaluating the cost of therapy for restenosis: considerations for brachytherapy

    International Nuclear Information System (INIS)

    Weintraub, William S.

    1996-01-01

    Costs have become increasingly important in medicine in recent years as demand for services has outstripped readily available resources. Clinical microeconomics offers an approach to understanding cost and outcomes in an environment of economic scarcity. In this article the types of costs and methods for determining cost are presented. In addition, methods for assessing outcome and outcome in relation to cost are developed. Restenosis after coronary angioplasty is a prime example of a clinical problem requiring economic evaluation. This is because it results in little serious morbidity except for recurrent chest pain, but it has serious economic consequences which occur some time after the original angioplasty. This makes the economic assessment of restenosis complicated. The application of health care microeconomic principles to brachytherapy for restenosis in the coronary arteries is presented

  3. Caracterización de la restenosis de stents coronarios convencionales y liberadores de medicamentos en pacientes incluidos en el registro DRug Eluting STent (DREST Characterization of conventional coronary stents restenosis and drug eluting stents in patients included in the Drug Eluting Stent Registry (DREST

    Directory of Open Access Journals (Sweden)

    Jorge A Arroyave C

    2012-06-01

    risk factor associated with stent restenosis of drug-eluting stents (p <0.002. We found smaller diameter of the vessel involved as well as smaller diameter of the implanted stent mainly in the drug-eluting stents associated with stent restenosis (p = 0.000. The focal pattern of stent restenosis was higher with drug eluting stents, while the diffuse pattern with standard stents (p = 0.000. The one-year survival was higher in patients with drug-eluting stent. Conclusions: The rates of stent restenosis and the related characteristics found are similar to those currently published. Dyslipidemia appears as a significant associated factor. The stent restenosis manifested as acute coronary syndrome in 60% of cases; it can not be regarded as a benign condition in this population.

  4. Hybrid strategy with a bioresorbable scaffold and a drug-coated balloon for diffuse coronary artery disease: the "no more metallic cages" multicentre pilot experience.

    Science.gov (United States)

    Ielasi, Alfonso; Miyazaki, Tadashi; Geraci, Salvatore; Testa, Luca; Abdel-Wahab, Mohamed; Kawamoto, Hiroyoshi; Ruparelia, Neil; Sato, Takao; Caramanno, Giuseppe; Bedogni, Francesco; Tespili, Maurizio; Colombo, Antonio; Latib, Azeem

    2016-04-08

    Our aim was to assess the feasibility and results of a hybrid approach with a bioresorbable scaffold (BRS) plus a drug-coated balloon (DCB) for the treatment of diffuse coronary artery disease (CAD). A retrospective analysis was performed on consecutive patients with diffuse de novo or in-stent restenosis treated with BRS implantation (larger proximal segment) and DCB inflation (smaller distal segment or bifurcation side branch). Endpoints were procedural success, then ischaemia-driven target lesion revascularisation (ID-TLR) and BRS/DCB segment thrombosis rates at follow-up. A total of 42 consecutive patients were treated with the hybrid strategy. Mean patient age was 62±1.02 years, while 12 (28.6%) patients were diabetics. Mean BRS and DCB length were 28.0±5.1 mm and 25.8±8.8 mm, respectively. Procedural success was obtained in all patients, but three (7.3%) patients required bail-out scaffolding for DCB-related dissection. At a median follow-up of 12 months (IQR: 6-18), there were no cases of cardiac death, target vessel myocardial infarction, or BRS/DCB segment thrombosis. ID-TLR occurred in two (4.7%) BRS-treated segments. Our data in consecutive patients with diffuse CAD suggest that a hybrid strategy using BRS and DCB in different segments of the diseased vessel is feasible and associated with encouraging clinical outcomes.

  5. Agreement of duplex ultrasonography vs. computed tomography angiography for evaluation of native and in-stent SFA re-stenosis--findings from a randomized controlled trial.

    Science.gov (United States)

    Langenberger, Herbert; Schillinger, Martin; Plank, Christina; Sabeti, Schila; Dick, Petra; Cejna, Manfred; Lammer, Johannes; Minar, Erich; Loewe, Christian

    2012-09-01

    Multidetector CT angiography (CTA) is a non-invasive imaging technique for evaluation of peripheral vascular disease. CTA might be particularly useful for assessment of intermediate- and long-term morphological outcome after endovascular treatment. Validation of CTA vs. the current imaging standard, colour Doppler ultrasonography (CDUS), for quantification of native and in-stent re-stenosis in the superficial femoral artery (SFA) is required. Seventy randomized patients who underwent stent implantation (n=47) or balloon angioplasty (n=23) underwent 6-month follow-up with CDUS and CTA. CTA was compared with CDUS in both sub-groups of patients in terms of binary re-stenosis (>50% lumen narrowing) and re-occlusion. Agreement between CTA and CDUS was assessed using Kappa (κ) statistics with 95% confidence intervals, and correlation coefficients. Binary re-stenosis was detected in 16/70 (22.9%) patients by CTA and 17/70 (24.3%) patients by CDUS (κ=0.88, 95% CI: 0.80-0.96). Re-stenosis rates after balloon angioplasty were 39.1% (9/23) on CTA and CDUS (κ=0.82, 95% CI: 0.66-0.98), and after stent implantation 14.9% (7/47) on CTA and 17.0% (8/47) on CDUS (κ=0.92, 95% CI: 0.84-1.00). Re-occlusions were detected in 3/70 (4.3%) patients by both CTA and CDUS (κ=0.65; 95% CI 0.54-0.76). Significant correlations (r=0.85, pSFA obstructions. CTA is an appropriate non-invasive imaging modality for follow-up after endovascular therapy. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  6. Hemodynamics in stented vertebral artery ostial stenosis based on computational fluid dynamics simulations.

    Science.gov (United States)

    Qiao, Aike; Dai, Xuan; Niu, Jing; Jiao, Liqun

    2016-01-01

    Hemodynamic factors may affect the potential occurrence of in-stent restenosis (ISR) after intervention procedure of vertebral artery ostial stenosis (VAOS). The purpose of the present study is to investigate the influence of stent protrusion length in implantation strategy on the local hemodynamics of the VAOS. CTA images of a 58-year-old female patient with posterior circulation transient ischemic attack were used to perform a 3D reconstruction of the vertebral artery. Five models of the vertebral artery before and after the stent implantation were established. Model 1 was without stent implantation, Model 2-5 was with stent protruding into the subclavian artery for 0, 1, 2, 3 mm, respectively. Computational fluid dynamics simulations based on finite element analysis were employed to mimic the blood flow in arteries and to assess hemodynamic conditions, particularly the blood flow velocity and wall shear stress (WSS). The WSS and the blood flow velocity at the vertebral artery ostium were reduced by 85.33 and 35.36% respectively after stents implantation. The phenomenon of helical flow disappeared. Hemodynamics comparison showed that stent struts that protruded 1 mm into the subclavian artery induced the least decrease in blood speed and WSS. The results suggest that stent implantation can improve the hemodynamics of VAOS, while stent struts that had protruded 1 mm into the subclavian artery would result in less thrombogenesis and neointimal hyperplasia and most likely decrease the risk of ISR.

  7. Third generation dual-source CT enables accurate diagnosis of coronary restenosis in all size stents with low radiation dose and preserved image quality.

    Science.gov (United States)

    Li, Yuehua; Yu, Mengmeng; Li, Wenbin; Lu, Zhigang; Wei, Meng; Zhang, Jiayin

    2018-01-18

    To investigate the diagnostic performance of low dose stent imaging in patients with large (≥ 3 mm) and small (source CT. Symptomatic patients suspected of having in-stent restenosis (ISR) were prospectively enrolled. Coronary computed tomography angiography (CCTA) and invasive coronary angiography (ICA) were performed within 1 month for correlation. Binary ISR was defined as an in-stent neointimal proliferation with diameter stenosis ≥ 50%. The radiation dose and image quality of CCTA were also assessed. Sixty-nine patients with 140 stents were ultimately included for analysis. The mean total radiation dose of CCTA was 1.3 ± 0.72 mSv in all patients and 0.95 ± 0.17 mSv in patients with high pitch acquisition. The overall diagnostic accuracy of CCTA stent imaging of patient-based, lesion-based and stent-based analysis was 95.7%, 94.1% and 94.3%, respectively. Further, the diagnostic accuracy of CCTA in the small calibre stent group (diameter source CT enables accurate diagnosis of coronary ISR of both large and small calibre stents. Low radiation dose could be achieved with preserved image quality. • Third-generation DSCT enables accurate diagnosis of coronary ISR of all size stents. • Low radiation dose could be achieved with preserved image quality. • The diagnostic accuracy of CCTA of small calibre stents was 88.5%.

  8. One-year results of the CRISTAL Trial, a randomized comparison of cypher sirolimus-eluting coronary stents versus balloon angioplasty for restenosis of drug-eluting stents.

    Science.gov (United States)

    Chevalier, Bernard; Moulichon, Robert; Teiger, Emmanuel; Brunel, Philippe; Metzger, Jean-Philippe; Pansieri, Michel; Carrie, Didier; Stoll, Hans-Peter; Wittebols, Kristel; Spaulding, Christian; Fajadet, Jean

    2012-12-01

     We compared the efficacy of the Cypher Select (Cordis Corporation, Bridgewater, NJ, USA) sirolimus-eluting stent (SES) versus balloon angioplasty (BA) in in-stent restenosis (ISR) of Taxus or Taxus Liberté paclitaxel-eluting stents (PES; Boston Scientific, Natick, MA, USA) or Cypher/Cypher Select SES. Optimal treatment strategies have not been identified for drug-eluting stent (DES) ISR. Patients with a native coronary artery SES or PES ISR were randomized to SES or BA. In addition, a control group included BMS ISR treated with SES. Angiographic control was performed at 12 months. 281 patients were enrolled. Significant differences favoring SES over BA were noted in immediate and net gain (1.39 ± 0.51 vs. 0.97 ± 0.54 mm, P < 0.0001 and 1.07 ± 0.69 vs. 0.49 ± 0.67 mm, P < 0.0001), 12-month mean luminal diameter (MLD; 2.14 ± 0.62 vs. 1.71 ± 0.55 mm, P < 0.0001) and percent diameter stenosis (%DS; 21 ± 19.24 vs. 29.82 ± 18.47, P = 0.001). There was no significant difference at 12 months between SES and BA in the primary end-point late lumen loss (LLL; 0.37 ± 0.57 vs.0.41 ± 0.63, P = 0.73) and in in-stent binary restenosis (11.1% vs. 14%, P = 0.59). Target-lesion revascularization (TLR) was numerically lower in patients treated with SES (5.9% vs. 13.1%, P = 0.097). There was no difference according to the initial DES. In contrast, significantly higher immediate and net gains and MLD were noted in the BMS control group treated by SES. In this angiographic randomized trial comparing SES and BA in SES or PES restenosis, 12 month MLD, immediate and net gain, and %DS favored SES whereas no difference was noted in LLL. Condensed abstract optimal treatment strategies have not been identified for sirolimus-(SES) or paclitaxel-eluting stent (PES) in-stent restenosis (ISR). We randomized patients with a native coronary artery SES or PES ISR to SES or BA. In addition, a control group included BMS ISR treated with SES. There

  9. Plasma levels of immunoinflammatory markers in De Novo coronary atherosclerosis and coronary restenosis postangioplasty

    Directory of Open Access Journals (Sweden)

    Alexandre Schaan de Quadros

    2001-05-01

    Full Text Available OBJECTIVE: To compare circulating plasma levels of immunoinflammatory markers in patients with known de novo coronary artery disease and patients with postangioplasty restenosis. METHODS: Using enzymatic immunoabsorbent assay, we measured plasma levels of soluble interleukin-2 receptosr, tumor necrosis factor alpha, and soluble tumor necrosis alpha receptors I and II in 11 patients with restenosis postcoronary angioplasty (restenosis group, in 10 patients with primary atherosclerosis (de novo group who were referred for coronary angiography because of stable or unstable angina, and in 9 healthy volunteers (control group. Levels of soluble interleukin-2 receptors were significantly higher in the de novo group compared with that in the restenosis and control groups. Levels were also higher in the restenosis group compared with that in the control group. Plasma levels of tumor necrosis alpha and receptor levels were significantly higher in the de novo group compared to with that in the restenosis and control groups, but levels in the restenosis group were not different from that in the controls. CONCLUSION: Coronary artery disease, either primary or secondary to restenosis, is associated with significant immunoinflammatory activity, which can be assessed by examining the extent of circulating plasma levels of inflammatory markers. Moreover, patients with de novo lesions appear to have increased inflammatory activity compared with patients with restenosis.

  10. Results of Prevention of REStenosis with Tranilast and its Outcomes (PRESTO) trial

    NARCIS (Netherlands)

    D.R. Holmes Jr (David); J.R. Granett (Jeffrey); J.J. Popma (Jeffrey); P.J. Fitzgerald (Peter); D. Fischman (David); J.J. Ferguson (James); A.M. Lincoff (Michael); S. Goldberg (Sheldon); J.A. Brinker; R. Chan; B.R. Davis (Barry); M. Poland; A.M. Zeiher (Andreas); J.T. Willerson (James); S.B. King 3rd (Spencer); L.M. Shapiro; M. Savage (Michael); J.M. Lablanche (Jean Marc); J.E. Tcheng (James); L. Grip (Lars); P.W.J.C. Serruys (Patrick)

    2002-01-01

    textabstractBACKGROUND: Restenosis after percutaneous coronary intervention (PCI) is a major problem affecting 15% to 30% of patients after stent placement. No oral agent has shown a beneficial effect on restenosis or on associated major adverse cardiovascular events. In limited trials, the oral

  11. Interleukin 10: A new risk marker for the development of restenosis after percutaneous coronary intervention

    NARCIS (Netherlands)

    Monraats, P.S.; Kurreeman, F.A.S.; Pons, D.; Sewgobind, V.D.K.D.; Vries, F.R. de; Zwinderman, A.H.; Maat, M.P.M. de; Doevendans, P.A.; Winter, R.J. de; Tio, R.A.; Waltenberger, J.; Huizinga, T.W.J.; Eefting, D.; Quax, P.H.A.; Frants, R.R.; Laarse, A. van der; Wall, E.E. van der; Jukema, J.W.

    2007-01-01

    Genetic factors appear to be important in the process of restenosis after percutaneous coronary intervention (PCI), as well as in inflammation, a pivotal factor in restenosis. An important mediator in the inflammatory response is interleukin (IL)-10. Our aim was to study whether genetic variants in

  12. Engineering Radioactive Stents for the Prevention of Restenosis

    International Nuclear Information System (INIS)

    Bruce Thomadsen; Nickles, Robert J.; Larry DeWerd; Douglass Henderson; Jonathan Nye; Wes Culberson; Stephen Peterson; Michael Meltsner; Liyong Lin

    2004-01-01

    Radiation has become an accepted treatment for the prevention of restenosis (re-blockage) of coronary arteries following angioplasty. Radioactive stents could be the easiest method of delivery for the radiation, although clinical trials were disappointing. One likely reason was the choice of P-32 as the radionuclide, which fails to match the biological needs of the problem. What radionuclide would perform best remains unknown. This project established the physical infrastructure necessary for a rational investigation to determine the optimum radiological characteristics for radioactive stents in the prevention of restenosis following angioplasty. The project investigated methods to activate coronary stents with radionuclides that spanned a range of energies and radiation types that could provide a mapping of the biological response. The project also provided calibration methods to determine the strength of the stents, an a process to calculate the dose distribution actually delivered to the patient's artery--quantities necessary for any future scientific study to improve the effectiveness of radioactive stents. Such studies could benefit the thousands of patients who receive angioplasty each year

  13. Engineering Radioactive Stents for the Prevention of Restenosis

    Energy Technology Data Exchange (ETDEWEB)

    Bruce Thomadsen; Robert J. Nickles; Larry DeWerd; Douglass Henderson; Jonathan Nye; Wes Culberson; Stephen Peterson; Michael Meltsner; Liyong Lin

    2004-09-10

    Radiation has become an accepted treatment for the prevention of restenosis (re-blockage) of coronary arteries following angioplasty. Radioactive stents could be the easiest method of delivery for the radiation, although clinical trials were disappointing. One likely reason was the choice of P-32 as the radionuclide, which fails to match the biological needs of the problem. What radionuclide would perform best remains unknown. This project established the physical infrastructure necessary for a rational investigation to determine the optimum radiological characteristics for radioactive stents in the prevention of restenosis following angioplasty. The project investigated methods to activate coronary stents with radionuclides that spanned a range of energies and radiation types that could provide a mapping of the biological response. The project also provided calibration methods to determine the strength of the stents, an a process to calculate the dose distribution actually delivered to the patient's artery--quantities necessary for any future scientific study to improve the effectiveness of radioactive stents. Such studies could benefit the thousands of patients who receive angioplasty each year.

  14. Late in-stent thrombosis following carotid angioplasty and stenting.

    Science.gov (United States)

    Buhk, Jan-Hendrik; Wellmer, Andreas; Knauth, Michael

    2006-05-23

    Acute in-stent thrombosis is a well-known complication of carotid angioplasty and stenting (CAS) and often due to resistance to or inadequate treatment with platelet-inhibiting agents. The authors report three cases of a delayed in-stent thrombosis after more than a week but less than 3 months after CAS. In all cases, the postprocedural antiplatelet regimen was discontinued to enable the treatment of a relevant comorbidity.

  15. Detecting Restenosis after Percutaneous Coronary Intervention Using Exercise-Stress Electrocardiogram Findings Including QT Dispersion

    Directory of Open Access Journals (Sweden)

    Bonpei Takase, MD

    2006-01-01

    Full Text Available Despite the advent of drug-eluting stents in Japan, bare metal stents or conventional balloon angioplasty are still indicated in some patients needing elective percutaneous coronary intervention (PCI and in patients with acute coronary syndrome if these patients develop side effects while taking ticlopidine. In such patients, restenosis is a problem that is difficult to diagnose. To investigate the comparative diagnostic accuracy of the exercise-stress electrocardiogram (ECG for detecting restenosis after PCI, we measured conventional ST-segment changes and QT dispersion during exercise-stress testing in 173 patients with elective PCI (63 ± 10 years old. Exercise-stress testing was performed 3 to 6 months after successful PCI, and restenosis was confirmed by follow-up coronary angiogram. There were 98 patients with a prior myocardial infarction (prior MI group and 76 patients with no prior myocardial infarction (no MI group. Restenosis was found in 45 patients (46% in the prior MI group and 26 patients (34% in the no MI group. Conventional ST-segment depression (>1:0 mm, J 60 ms indicating exercise-induced myocardial ischemia had a sensitivity of around 50% and a specificity of around 70% for diagnosing restenosis in both groups. In the prior MI group, QT dispersion was increased by exercise-stress testing in both patients with and without restenosis, whereas in the no MI group, QT dispersion increased only in patients with restenosis. With a cut-off value of >60 ms, QT dispersion had a sensitivity of 54% and a specificity of 68% for detecting restenosis in the no MI group; these values were comparable to those seen with conventional ST-segment changes. In conclusion, due to its low cost, exercise-stress ECG remains useful for diagnosing restenosis following PCI if the clinician understands its limited sensitivity and specificity. The presence of a prior MI must be considered when QT dispersion during exercise-stress testing is used for

  16. Optimal conjugation of catechol group onto hyaluronic acid in coronary stent substrate coating for the prevention of restenosis.

    Science.gov (United States)

    Lih, Eugene; Choi, Seul Gi; Ahn, Dong June; Joung, Yoon Ki; Han, Dong Keun

    2016-01-01

    Although endovascular stenting has been used as an interventional therapy to treat cardio- and cerebro-vascular diseases, it is associated with recurrent vascular diseases following stent thrombosis and in-stent restenosis. In this study, a metallic stent was coated with dopamine-conjugated hyaluronic acid with different ratios of catechol group to improve hemocompatibility and re-endothelialization. Especially, we were interested in how much amount of catechol group is appropriate for the above-mentioned purposes. Therefore, a series of dopamine-conjugated hyaluronic acid conjugates with different ratios of catechol group were synthesized via a carbodiimide coupling reaction. Dopamine-conjugated hyaluronic acid conjugates were characterized with 1 H-nuclear magnetic resonance and Fourier transform infrared spectroscopy, and the amount of catechol group in dopamine-conjugated hyaluronic acid was measured by ultraviolet spectrometer. Co-Cr substrates were polished and coated with various dopamine-conjugated hyaluronic acid conjugates under pH 8.5. Dopamine-conjugated hyaluronic acid amounts on the substrate were quantified by micro-bicinchoninic acid assay. Surface characteristics of dopamine-conjugated hyaluronic-acid-coated Co-Cr were evaluated by water contact angle, scanning electron microscopy, and atomic force microscopy. The hemocompatibility of the surface-modified substrates was assessed by protein adsorption and platelet adhesion tests. Adhesion and activation of platelets were confirmed with scanning electron microscopy and lactate dehydrogenase assay. Human umbilical vein endothelial cells were cultured on the substrates, and the viability, adhesion, and proliferation were investigated through cell counting kit-8 assay and fluorescent images. Obtained results demonstrated that optimal amounts of catechol group (100 µmol) in the dopamine-conjugated hyaluronic acid existed in terms of various properties such as hemocompatibility and cellular responses.

  17. Exercise radionuclide ventriculography to detect restenosis following coronary angioplasty

    International Nuclear Information System (INIS)

    De Puey, E.G.; Leatherman, L.L.; Dear, W.E.; Leachman, R.D.; Massin, E.K.; Mathur, V.S.; Burdine, J.A.

    1984-01-01

    Forty one patients (pts) underwent semiupright exercise gated radionuclide ventriculography (EGRNV) before, within 3 d after single vessel transluminal coronary angioplasty (TCA), and 4 to 12 mos later, at which time follow-up cardiac catheterization was also performed. Prior to TCA 76% of pts had abnormal EGRNV, as defined by a failure to increase ejection fraction (EF) by 5 points or the development of a new regional wall motion abnormality. Stenosis was reduced from 90 +- 7% to 18 +- 17%. Early after TCA, exercise duration and maximum double product increased (p's 20% but <50%; Group III (n=8): ≥ 50%] Pts with abnormal EGRNV early after TCA were demonstrated to have a greater percent increase in stenosis at late follow-up than pts with normal EGRNV (41 +- 30% vs 19 +- 25%, p<.001). Early after TCA EGRNV was abnormal in 5% of Group I pts vs 75% in Group III (p<.01), and EF increased to a greater degree during exercise in Group I pts (+11.3 +- 7.5 vs +3.5 +- 6.5 points, p<.01). At 4-12 mos EGRNV was abnormal in 27% of Group I vs 88% of Group III (p<.01), and during exercise EF increased in Group I pts (+11.8 +- 7.8 points) but decreased in Group III (-1.9 +- 8.7 points) (p<.0005). The accuracy of abnormal EGRNV in predicting ≥ 50% restenosis was 73% early post-TCA and 77% at 4-12 mos. The authors conclude that EGRNV is a valuable test to verify the success of TCA and to detect subsequent restenosis

  18. Early detection of restenosis after successful percutaneous transluminal coronary angioplasty by exercise-redistribution Thallium scintigraphy

    NARCIS (Netherlands)

    W. Wijns (William); P.W.J.C. Serruys (Patrick); J.H.C. Reiber (Johan); P.J. de Feyter (Pim); M.J.B.M. van den Brand (Marcel); M.L. Simoons (Maarten); P.G. Hugenholtz (Paul)

    1985-01-01

    textabstractThe value of exercise testing and thallium scintigraphy in predicting recurrence of angina pectoris and restenosis after a primary successful transluminal coronary angioplasty (PTCA) was prospectively evaluated. In 89 patients, a symptom-limited exercise electrocardiogram (ECG) and

  19. Coronary collaterals and risk for restenosis after percutaneous coronary interventions: a meta-analysis

    Directory of Open Access Journals (Sweden)

    Meier Pascal

    2012-06-01

    Full Text Available Abstract Background The benefit of the coronary collateral circulation (natural bypass network on survival is well established. However, data derived from smaller studies indicates that coronary collaterals may increase the risk for restenosis after percutaneous coronary interventions. The purpose of this systematic review and meta-analysis of observational studies was to explore the impact of the collateral circulation on the risk for restenosis. Methods We searched the MEDLINE, EMBASE and ISI Web of Science databases (2001 to 15 July 2011. Random effects models were used to calculate summary risk ratios (RR for restenosis. The primary endpoint was angiographic restenosis > 50%. Results A total of 7 studies enrolling 1,425 subjects were integrated in this analysis. On average across studies, the presence of a good collateralization was predictive for restenosis (risk ratio (RR 1.40 (95% CI 1.09 to 1.80; P = 0.009. This risk ratio was consistent in the subgroup analyses where collateralization was assessed with intracoronary pressure measurements (RR 1.37 (95% CI 1.03 to 1.83; P = 0.038 versus visual assessment (RR 1.41 (95% CI 1.00 to 1.99; P = 0.049. For the subgroup of patients with stable coronary artery disease (CAD, the RR for restenosis with 'good collaterals' was 1.64 (95% CI 1.14 to 2.35 compared to 'poor collaterals' (P = 0.008. For patients with acute myocardial infarction, however, the RR for restenosis with 'good collateralization' was only 1.23 (95% CI 0.89 to 1.69; P = 0.212. Conclusions The risk of restenosis after percutaneous coronary intervention (PCI is increased in patients with good coronary collateralization. Assessment of the coronary collateral circulation before PCI may be useful for risk stratification and for the choice of antiproliferative measures (drug-eluting stent instead bare-metal stent, cilostazol.

  20. Drug-Eluting Balloon versus New-Generation Drug-Eluting Stent for the Treatment of In-Stent Restenosis: An Updated Systematic Review and Meta-Analysis

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    Kong-Yong Cui

    2018-01-01

    Conclusions: The current meta-analysis showed that DEB and new-generation DES had comparable safety and efficacy for the treatment of ISR in RCTs. However, treatment with DEB was associated with higher risk of all-cause mortality in the real-world nonrandomized studies.

  1. Usefulness of Eosinophil-Lymphocyte Ratio to Predict Stent Restenosis

    Directory of Open Access Journals (Sweden)

    Mehmet Zihni Bilik

    2016-06-01

    Full Text Available Objective: Stent restenosis (SR is an important compli­cation of percutaneous coronary intervention. There are many studies explored the relation of eosinophils with SR, however, there is no data about relationship between eo­sinophil-lymphocyte ratio (ELR and SR. In this study we aimed to investigate the relationship between the value of ELR on admission and SR. Methods: The study was included 314 patients who had been applied a coronary stent implantation and they were admitted to cardiology clinic with stabile angina and un­derwent repeat coronary angiography. The data obtained from patients were analyzed retrospectively. The patient group was consisted of 197 patients who were diagnosed as SR, and the control group was consisted of 117 pa­tients whose stents were patent angiographically. Results: The groups were similar in terms of age, gender, hypertension, diabetes mellitus, LDL-C, HDL-C, platelet count, platelet-lymphocyte ratio (PLR, hemoglobin and left ventricle ejection fraction (LVEF. White blood cell (WBC, neutrophil, eosinophil, C-reactive protein (CRP, ELR and neutrophil-lymphocyte ratio (NLR on admission were higher in the SR group compared to the controls. All patients were categorized into two groups according to ELR values and SR was more frequent in the high ELR group compared to low ELR group. An ELR value of ≥0.745 predicted SR with 64% sensitivity and 61% specif­ity. Conclusion: In this study ELR was found statistically higher in SR patients compared to the controls. Accord­ing to our data ELR as an inexpensive and easy method, may contribute to determination of high risk patients and increased ELR can be used as a predictor of SR.

  2. Beta-radiation therapy for long lesions in native coronary vessels A matched comparison between de novo and in-stent restenotic lesions

    International Nuclear Information System (INIS)

    Stankovic, Goran; Orlic, Dejan; Di Mario, Carlo; Corvaja, Nicola; Airoldi, Flavio; Chieffo, Alaide; Amato, Antonio; Orecchia, Roberto; Colombo, Antonio

    2003-01-01

    Objective: The purpose of this study was to evaluate effectiveness and to compare clinical outcome of intracoronary beta-radiation to treat long lesions (>20 mm) in patients with de novo stenosis vs. patients with in-stent restenosis (ISR). Methods: A matched comparison of 44 patients with 63 de novo lesions and 48 patients with 63 ISR lesions (>20 mm) treated with intracoronary beta-radiation was performed. Results: Stents were implanted in 65.1% of de novo and 19% of ISR lesions (P=.001). Radiation doses delivered were 17.2±3.0 vs. 20.3±3.0 Gy at 2 mm from the source center for de novo and ISR lesions. There was no difference in the incidence of in-hospital events. Clinical follow-up at 16.4±6.7 months showed no difference in major adverse cardiac events (MACE) between de novo and ISR patients (27.3% vs. 25%, P=.8). Late total occlusions (LTOs) occurred in eight patients (four in each group) treated with stents at the time of radiation and after discontinuation of ticlopidine. By multivariate analysis, stent implantation was the only predictor of late occlusions (OR 8.25, 95% CI 1.73-38.46, P<.008). Restenosis rates were similar for de novo and ISR lesions (29.3% vs. 23.2%, P=.46), as well as target lesion revascularization (TLR) and target vessel revascularization (TVR) rates (22.7% vs. 22.9% and 29.5% vs. 29.2%, respectively). Conclusions: Intracoronary beta-radiation gives comparable results when used to treat de novo or ISR lesions provided new stent implantation can be avoided. Long-term combined antiplatelet therapy is mandatory for patients who receive new stents at the time of radiation treatment

  3. Study on the application of big cup membranate stent on restenosis after stenting for carcinoma of esophago cardia

    International Nuclear Information System (INIS)

    Wang Xiuping; Yao Zhongqiang; Liu Jian; Zhang Yan

    2007-01-01

    Objective: To evaluate the clinical value of self-designed big cup membranate stent on restenosis after stenting for carcinoma of esophago-cardia. Methods: 12 cases of restenosis after stenting for carcinoma of esophago-cardia were involved in the study. Self-designed big cup membranate stent made by Nanjing Weichuang Company (the length of the cup was 3.5 cm)was placed into the constricted stent under guidance of fluoroscopy. Clinical effect, restenosis, and complications were observed during followed up. Results: All the 12 cases of big cup membranat stent placement went along smoothly without indigitation of the cup of the stent. Follow-up of 1.5-8 months showed that 2 cases developed severe restenosis on the big cup of the stem, resulting in third grade difficult deglutition. Among them, one occurred 1 month after stenting, caused by hyperplasia of large amount of granulation tissue; another occurred 6 months after stenting, caused by growth of tumor tissue. 3 cases developed mild to moderate restenosis, 2.3-7 months (mean: 4.6 months) after stenting, with result of first grade difficult deglutition. The remaining 7 cases (mean 5.6 months follow-up) did not have difficulty during deglutition. Conclusions: Application of big cup membranate stent on restenosis after stenting for carcinoma of esophago-cardia can effectively prevent the stent from moving downwards and thus lower down the rate of restenosis, and postpone the occurrence of restenosis. (authors)

  4. Left-main restenosis in the DES era-a call for action.

    Science.gov (United States)

    di Palma, Gaetano; Cortese, Bernardo

    2017-11-10

    Percutaneous treatment of the unprotected left main trunk (ULM), defined as a vessel without patent bypass graft either to the left circumflex (LCX) or left anterior descending (LAD) artery, has gained a precise role thanks to recent scientific evidence. Although new generation drug-eluting stents have already proven to be safer, there is still a consistent risk of restenosis and late adverse events. The optimal management of a ULM restenosis is still debated. Here we aim at presenting a review of the available data in literature and show our choice for treating it. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Metabolic syndrome and risk of restenosis in patients undergoing percutaneous coronary intervention

    NARCIS (Netherlands)

    Wouterjukema, J; Monraats, PS; Zwinderman, AH; De Maat, MPM; Kastelein, JJP; Doevendans, PAF; De Winter, RJ; Tio, RA; Frants, RR; Van der Laarse, A; Van der Wall, EE; Jukema, JW

    OBJECTIVE - Patients with metabolic syndrome have increased risk of cardiovascular events. The number of patients With Metabolic syndrome is rapidly increasing, and these patients Often need revascularization. However, only limited data are available on the effect of metabolic syndrome on restenosis

  6. Drug-eluting stents studies in mice: do we need atherosclerosis to study restenosis?

    NARCIS (Netherlands)

    Pires, Nuno M. M.; Jukema, J. Wouter; Daemen, Mat J. A. P.; Quax, Paul H. A.

    2006-01-01

    In 2001, the first human study with drug-eluting stents (DES) was published showing a nearly complete abolition of restenosis by using a sirolimus-eluting stent. This success was very encouraging to test new compounds in combination with the DES platform. Nevertheless, several other anti-restenotic

  7. Platelet deposition at angioplasty sites and its relation to restenosis in human iliac and femoropopliteal arteries

    International Nuclear Information System (INIS)

    Minar, E.; Ehringer, H.; Ahmadi, R.; Dudczak, R.; Leitha, T.; Koppensteiner, R.; Jung, M.; Stuempflen, A.

    1989-01-01

    The amount and time course of platelet accumulation at angioplasty sites and influence of these platelets on restenosis after percutaneous transluminal angioplasty (PTA) in peripheral arteries were determined in 92 patients, who received either a high or low dose of aspirin. Platelet deposition was quantitated by means of dual-radiotracer scintigraphy and calculation of a platelet accumulation index (PAI). The PAI was higher (P less than .05) 4-6 hours after PTA compared with that on subsequent days. There was a trend toward greater platelet accumulation in vessels with extensive dissection. Platelet accumulation at the PTA site occurred with both doses of aspirin, with no differences between the two dosage groups. Twenty-one of 67 patients who underwent PTA in the femoropopliteal segment developed restenosis during a median follow-up of 14 months. The median PAI at 4-6 and 22-24 hours after PTA was significantly less in these 21 patients than in the 46 without restenosis. The data suggest that use of antiplatelet agents to prevent platelet deposition after PTA may not be useful for prevention of restenosis

  8. Models and Analysis of Atherosclerosis, Restenosis, and Aneurysm Formation in the Mouse

    NARCIS (Netherlands)

    de Waard, Vivian; Gijbels, Marion J. J.; Lutgens, Esther; de Winther, Menno P. J.; de Vries, Carlie J. M.

    2012-01-01

    Atherosclerosis is considered a chronic inflammatory condition of the vessel wall and involves a high chronic concentration of low-density lipoprotein (LDL) in blood. In humans, restenosis develops after intravascular interventions such as angioplasty and stent placement to treat atherosclerosis,

  9. Impact of cutting balloon angioplasty (CBA) prior to bare metal stenting on restenosis.

    Science.gov (United States)

    Ozaki, Yukio; Yamaguchi, Tetsu; Suzuki, Takahiko; Nakamura, Masato; Kitayama, Michihiko; Nishikawa, Hideo; Inoue, Teruo; Hara, Kazuhiro; Usuba, Fumihiko; Sakurada, Masami; Awano, Kojiro; Matsuo, Hitoshi; Ishiwata, Sugao; Yasukawa, Tatsuya; Ismail, Tevfik F; Hishida, Hitoshi; Kato, Osamu

    2007-01-01

    While stent restenosis and late thrombosis still occur even with drug-eluting-stents (DES), there remains a need to explore other strategies for preventing restenosis. Five hundred and twenty-one patients were randomized: 260 to cutting-balloon angioplasty (CBA) before bare-metal stent (CBA-BMS) and 261 to balloon-angioplasty (BA) before BMS (BA-BMS). Intravascular ultrasound (IVUS)-guided procedures were performed in 279 (54%) patients and angiographic guidance was used in the remainder. Minimal lumen diameter was significantly greater in CBA-BMS than BA-BMS (2.65+/-0.40 mm vs 2.52+/-0.4 mm, p<0.01) and % diameter stenosis (%DS)-post was less in CBA-BMS than BA-BMS (14.0+/-5.9% vs 16.3+/-6.8%, p<0.01). %DS-follow-up was subsequently less in CBA-BMS than BA-BMS (32.4+/-15.1% vs 35.4+/-15.3%, p<0.05) associated with lower rates of restenosis in CBA-BMS than BA-BMS (11.8% vs 19.6%, p<0.05) and less target lesion revascularization (TLR) in CBA-BMS than BA-BMS (9.6% vs 15.3%, p<0.05). Patients were divided into 4 groups based on the device used before stenting and IVUS use (IVUS-CBA-BMS: 137 patients; Angio-CBA-BMS: 123; IVUS-BA-BMS: 142; and Angio-BA-BMS: 119). At follow-up IVUS-CBA-BMS had a significantly lower restenosis rate (6.6%) than Angio-CBA-BMS (17.9%), IVUS-BA-BMS (19.8%) and Angio-BA-BMS (18.2%, p<0.05). Restenosis and TLR were significantly lower in CBA-BMS than BA-BMS. This favorable outcome was achieved because of the lower restenosis rate conferred by the IVUS-guided-CBA-BMS strategy (6.6%). The restenosis rates obtained with this strategy were comparable to those achieved with DES.

  10. Astro research fellowship: low dose radiation to prevent restenosis after angioplasty

    International Nuclear Information System (INIS)

    Rege, Sheila; Razavi, Mahmood; Fessenden, Kali; Ziegler, Werner; Gomez, Antoinette; Smathers, James; Withers, Rodney

    1997-01-01

    Purpose: To determine the optimal time to deliver a single dose of external radiation therapy (12 Gy) postoperatively following balloon angioplasty (on same day, day 2 or day 4) to prevent restenosis in a non-stented swine model. To model an endovascular radioactive source for prevention of restenosis in the same animal model. Materials and Methods: Both external iliac arteries in eleven red duroc swine were injured using balloon overdilation (3 inflations, 60 secs. each, 16 psi), and the first five were additionally injured using denudation. One artery in each animal was then irradiated using anteroposterior and posterioranterior fields using Co-60 with 12 Gy prescribed to the midplane, with the other artery serving as a control. Irradiation was delivered on the same day, day 2 or day 4. Animals were sacrificed 3 months following injury, and histomorphometric analysis was performed. Additionally, a prototype endovascular beta source was designed and manufactured for clinical testing, based on Monte Carlo estimations. Results: Neointima formation was noted in both radiated and control arteries. The mean neointimal thickness in the radiated and control arteries was 116 ± 39 μm and 131 ± 47 μm respectively. Time of radiation delivery did not have a significant effect in preventing restenosis. Physical measurements of the endovascular source are in progress using a water based phantom. Animal testing will commence on ten red duroc swine. Conclusion: External radiation at this low dose does not appear to prevent restenosis in an unstented animal model. We hope to begin animal experiments using an endovascular source to prevent restenosis

  11. Blood flow in stented coronary artery: numerical fluid dynamics analysis.

    Science.gov (United States)

    Bénard, N; Perrault, R; Coisne, D

    2004-01-01

    Recent generalization of stent implantation in interventional cardiology require full understanding of blood flow cartography. Interdepency between fluid stresses and in vivo cells covering lumen artery are regularly accused to be one of the instigator of neointimal proliferation (thickening of the inner layer of blood vessels) and mid-term restenosis. This study purpose to numericaly investigate the three dimensional flow in vicinity of an endoprothesis. We used a finite element method to simulate a steady flow of non-Newtonian fluid in a coronary artery using a rigid wall approximation. Results on the velocities, wall shear stress and wall shear stress gradients are presented. Theses simulations allow identification of stagnation site and low wall shear stress area that may be prone to clot formation and neointimal hyperplasia. Intra stent flow knowledge can potentially contribute to optimization of prothesis design and decreasing second intervention rate.

  12. Mitral restenosis in the early postoperative period of a patient with systemic lupus erythematosus

    Directory of Open Access Journals (Sweden)

    Pomerantzeff Pablo Maria Alberto

    1999-01-01

    Full Text Available A forty eight year old woman, who had undergone mitral comissurotomy and subsequently developed early restenosis, presented with major comissural fusion and verrucous lesions on the cuspid edges of the mitral valve, with normal subvalvar apparatus. Patient did well for the first six months after surgery when she began to present dyspnea on light exertion. A clinical diagnosis of restenosis was made, which was confirmed by an echocardiogram and cardiac catheterization. She underwent surgery, and a stenotic mitral valve with verrucous lesions suggesting Libman-Sacks' endocarditis was found. Because the diagnosis of systemic lupus erythematosus (SLE had not been confirmed at that time, a bovine pericardium bioprosthesis (FISICS-INCOR was implanted. The patient did well in the late follow-up and is now in NYHA Class I .

  13. Mitral restenosis in the early postoperative period of a patient with systemic lupus erythematosus.

    Science.gov (United States)

    Pomerantzeff, P M; Corrêa, J D; Brandão, C M; de Assis, R V; Jatene, A D

    1999-04-01

    A forty-eight year old woman, who had undergone mitral comissurotomy and subsequently developed early restenosis, presented with major comissural fusion and verrucous lesions on the cuspid edges of the mitral valve, with normal subvalvar apparatus. Patient did well for the first six months after surgery when she began to present dyspnea on light exertion. A clinical diagnosis of restenosis was made, which was confirmed by an echocardiogram and cardiac catheterization. She underwent surgery, and a stenotic mitral valve with verrucous lesions suggesting Libman-Sacks' endocarditis was found. Because the diagnosis of systemic lupus erythematosus (SLE) had not been confirmed at that time, a bovine pericardium bioprosthesis (FISICS-INCOR) was implanted. The patient did well in the late follow-up and is now in NYHA Class I.

  14. Oversizing and Restenosis with Self-Expanding Stents in Iliofemoral Arteries

    International Nuclear Information System (INIS)

    Saguner, Ardan M.; Traupe, Tobias; Räber, Lorenz; Hess, Nina; Banz, Yara; Saguner, Arhan R.; Diehm, Nicolas; Hess, Otto M.

    2012-01-01

    Purpose: Uncoated self-expanding nitinol stents (NS) are commonly oversized in peripheral arteries. In current practice, 1-mm oversizing is recommended. Yet, oversizing of NS may be associated with increased restenosis. To provide further evidence, NS were implanted in porcine iliofemoral arteries with a stent-to-artery-ratio between 1.0 and 2.3. Besides conventional uncoated NS, a novel self-expanding NS with an antiproliferative titanium-nitride-oxide (TiNOX) coating was tested for safety and efficacy. Methods: Ten uncoated NS and six TiNOX-coated NS (5–6 mm) were implanted randomly in the iliofemoral artery of six mini-pigs. After implantation, quantitative angiography (QA) was performed for calculation of artery and minimal luminal diameter. Follow-up was performed by QA and histomorphometry after 5 months. Results: Stent migration, stent fracture, or thrombus formation were not observed. All stents were patent at follow-up. Based on the location of the stent (iliac/femoral) and the stent-to-artery-ratio, stent segments were divided into “normal-sized” (stent-to-artery-ratio < 1.4, n = 12) and “oversized” (stent-to-artery-ratio ≥ 1.4, n = 9). All stent segments expanded to their near nominal diameter during follow-up. Normal-sized stent segments increased their diameter by 6% and oversized segments by 29%. A significant correlation between oversizing and restenosis by both angiography and histomorphometry was observed. Restenosis rates were similar for uncoated NS and TiNOX-coated NS. Conclusions: TiNOX-coated NS are as safe and effective as uncoated NS in the porcine iliofemoral artery. All stents further expand to near their nominal diameter during follow-up. Oversizing is linearly and positively correlated with neointimal proliferation and restenosis, which may not be reduced by TiNOX-coating.

  15. Optimization of cardiovascular stent against restenosis: factorial design-based statistical analysis of polymer coating conditions.

    Directory of Open Access Journals (Sweden)

    Gayathri Acharya

    Full Text Available The objective of this study was to optimize the physicodynamic conditions of polymeric system as a coating substrate for drug eluting stents against restenosis. As Nitric Oxide (NO has multifunctional activities, such as regulating blood flow and pressure, and influencing thrombus formation, a continuous and spatiotemporal delivery of NO loaded in the polymer based nanoparticles could be a viable option to reduce and prevent restenosis. To identify the most suitable carrier for S-Nitrosoglutathione (GSNO, a NO prodrug, stents were coated with various polymers, such as poly (lactic-co-glycolic acid (PLGA, polyethylene glycol (PEG and polycaprolactone (PCL, using solvent evaporation technique. Full factorial design was used to evaluate the effects of the formulation variables in polymer-based stent coatings on the GSNO release rate and weight loss rate. The least square regression model was used for data analysis in the optimization process. The polymer-coated stents were further assessed with Differential scanning calorimetry (DSC, Fourier transform infrared spectroscopy analysis (FTIR, Scanning electron microscopy (SEM images and platelet adhesion studies. Stents coated with PCL matrix displayed more sustained and controlled drug release profiles than those coated with PLGA and PEG. Stents coated with PCL matrix showed the least platelet adhesion rate. Subsequently, stents coated with PCL matrix were subjected to the further optimization processes for improvement of surface morphology and enhancement of the drug release duration. The results of this study demonstrated that PCL matrix containing GSNO is a promising system for stent surface coating against restenosis.

  16. Flow disturbances in stent-related coronary evaginations

    DEFF Research Database (Denmark)

    Radu, Maria D; Pfenniger, Aloïs; Räber, Lorenz

    2014-01-01

    Aims: Angiographic ectasias and aneurysms in stented segments have been associated with late stent thrombosis. Using optical coherence tomography (OCT), some stented segments show coronary evaginations reminiscent of ectasias. The purpose of this study was to explore, using computational fluid......-dynamic (CFD) simulations, whether OCT-detected coronary evaginations can induce local changes in blood flow. Methods and results: OCT-detected evaginations are defined as outward bulges in the luminal vessel contour between struts, with the depth of the bulge exceeding the actual strut thickness. Evaginations...... can be characterised cross ectionally by depth and along the stented segment by total length. Assuming an ellipsoid shape, we modelled 3-D evaginations with different sizes by varying the depth from 0.2-1.0 mm, and the length from 1-9 mm. For the flow simulation we used average flow velocity data from...

  17. Endovascular brachytherapy prevents restenosis after femoropopliteal angioplasty: results of the Vienna-3 randomised multicenter study

    International Nuclear Information System (INIS)

    Pokrajac, Boris; Poetter, Richard; Wolfram, Roswitha M.; Budinsky, Alexandra C.; Kirisits, Christian; Lileg, Brigitte; Mendel, Helmuth; Sabeti, Schila; Schmid, Rainer; Minar, Erich

    2005-01-01

    Background and purpose: The aim of the trial was to investigate the effect of Iridium-192 gamma endovascular brachytherapy on reduction of restenosis after femoropopliteal angioplasty. Patients and methods: Between Oct, 1998 and Jul, 2001 a total of 134 patients have been randomized after successful angioplasty to brachytherapy or sham irradiation in a prospective, randomized, multicenter, double blind controlled trial. Patients with de novo lesion of at least 5 cm or recurrent lesion of any length after prior angioplasty have been enrolled. Brachytherapy was performed with 7 F centering catheter. Mean lesion length was 9.1 cm (1.5-25 cm) and mean intervention length 13.6 cm (4-27.5 cm) in brachytherapy cohort. Results: In placebo cohort mean lesion length was 10.3 cm (2-25 cm) and mean intervention length 14.1 cm (2-29 cm). A dose of 18 Gy was prescribed 2 mm from the surface of centering balloons. Analyzed (based on angiography) on intention to treat basis the binary restenosis rate at 12 months was 41.7% (28/67) in brachytherapy cohort and 67.1% (45/67) in placebo cohort (χ 2 test, P 30% residual stenosis after angioplasty) have been 23.4% in the brachytherapy and 53.3% in the placebo group (P<0.05), respectively. The cumulative patency rates after 24 months on intention to treat analysis were 54% in the brachytherapy and 27% in the placebo group (P<0.005). Corresponding data for as treated analysis were 77% in the brachytherapy and 39% in the placebo group (P<0.001). Late thrombosis was not seen. Conclusions: Significant reduction of restenosis rate was obtained with endovascular gamma brachytherapy after femoropopliteal angioplasty

  18. Restenosis of the sigmoid sinus after stenting for treatment of intracranial venous hypertension: case report

    International Nuclear Information System (INIS)

    Tsumoto, T.; Miyamoto, T.; Shimizu, M.; Inui, Y.; Nakakita, K.; Hayashi, S.; Terada, T.

    2003-01-01

    We report what we believe to be the first case of restenosis of the sigmoid sinus after stenting, in a 42-year-old man with an arteriovenous malformation with progressive right hemiparesis secondary to venous hypertension. Angiography revealed severe stenosis of the left sigmoid sinus, which was dilated with a self-expandable stent. Six months after the procedure, however, the sinus was again severely stenosed. Intravascular sonography revealed intimal proliferation in the stented sinus. It was dilated percutaneously, and the venous pressure decreased from 51 to 33 mmHg. On sonography, the intimal tissue decreased in thickness and the diameter of the stent enlarged a little. (orig.)

  19. Angiographic Findings of the Multicenter Randomized Study With the Sirolimus-Eluting Bx Velocity Balloon-Expandable Stent (RAVEL) : Sirolimus-Eluting Stents Inhibit Restenosis Irrespective of the Vessel Size

    NARCIS (Netherlands)

    E.S. Regar (Eveline); M. Degertekin (Muzaffer); M-C. Morice (Marie-Claude); K. Tanabe (Kengo); E. Wülfert (Egon); C. Disco (Clemens); C. Holubarsch; J-L. Guermonprez (Jean-Leon); W. Wijns (William); A. Bartorelli (Antonio); P.W.J.C. Serruys (Patrick); C.H. Bode (Christoph); C. Constantini (Constantino)

    2002-01-01

    markdownabstractBACKGROUND: Restenosis remains the major limitation of coronary catheter-based intervention. In small vessels, the amount of neointimal tissue is disproportionately greater than the vessel caliber, resulting in higher restenosis rates. In the Randomized Study With the

  20. Predictive factors for in-stent late loss and coronary lesion progression in patients with type 2 diabetes mellitus randomized to rosiglitazone or placebo.

    Science.gov (United States)

    Finn, Aloke V; Oh, Jae S; Hendricks, Michael; Daher, Maureen; Cagliero, Enrico; Byrne, Raphael M; Nadelson, Jeffrey; Crimins, Johanna; Kastrati, Adnan; Schömig, Albert; Bruskina, Olga; Palacios, Igor; John, Michael C; Gold, Herman K

    2009-02-01

    Type 2 diabetics (DM2) are at increased risk for restenosis as well as nonculprit coronary artery lesion (NCCL) progression. Rosiglitazone (RSG) favorably modifies many of the altered biologic processes in DM2, although recent reports have questioned its safety. We conducted a double-blind randomized trial to assess the effects of RSG versus placebo on in-stent late lumen loss (LL) and angiographic progression of NCCL. A total of 65 DM2 were randomized to RSG (4 mg/d) (n = 32) or placebo (n = 33) at the time of stenting and underwent clinical and laboratory analysis at 1 and 4 months and 8-month angiography (n = 46 patients). Rapid angiographic progression (RAP) was defined as > or =20% diameter reduction of preexisting NCCL by quantitative coronary angiography, or a new narrowing > or =30%. Mean LL in RSG (n = 33 lesions) was not different from that of placebo (0.62 +/- 0.59 vs 0.70 +/- 0.67, P = NS). Seven (13.5%) of 52 NCCLs have RAP in RSG versus 9 (16.1%) of 56 in placebo (P = NS). High-sensitivity C-reactive protein (hs-CRP) was the only predictor of RAP. Patients with a 120-day hs-CRP > or =75th percentile had an OR of 7.35 (95% CI 2.35-23) for RAP versus those below. Although RSG treatment also lowered log (hs-CRP) at 4 months (RSG 0.10 +/- 0.37 vs placebo 0.26 +/- 0.49, P = .06), it did not decrease the likelihood of plaque progression while also raising LDL and N-terminal brain naturetic peptide. Rosiglitazone appears not to lower LL or reduce angiographic progression of NCCL in DM2 and had complex effects on markers of cardiac risk.

  1. Zotarolimus-eluting stent for the treatment of recurrent, severe carotid artery in-stent stenosis in the TARGET-CAS population.

    Science.gov (United States)

    Tekieli, Lukasz; Pieniazek, Piotr; Musialek, Piotr; Kablak-Ziembicka, Anna; Przewlocki, Tadeusz; Trystula, Mariusz; Moczulski, Zbigniew; Dzierwa, Karolina; Paluszek, Piotr; Podolec, Piotr

    2012-06-01

    To evaluate the safety and efficacy of a balloon-mounted drug-eluting stent (DES) for recurrent carotid in-stent stenosis (ISS). As part of our targeted carotid artery stenting (TARGET-CAS) protocol, neurological and ultrasound evaluations have been performed at 3, 6, and 12 months and then annually since 2001 in all carotid stent patients. For angiographically-confirmed >70% ISS, balloon angioplasty was performed as a first-line treatment. Recurrent ISS was treated with a 4.0-mm zotarolimus-eluting coronary stent (ZES) that was postdilated according to intravascular ultrasound imaging. Among the 1350 neuroprotected CAS procedures performed between January 2001 and March 2011, there were 7 (0.52%) patients (5 men; ages 51-72 years), all neurologically asymptomatic, with >70% recurrent ISS that occurred at 5 to 11 months after the initial balloon angioplasty treatment for ISS. ZES implantation under distal embolic protection was technically successful and uncomplicated. Angiographic stenosis was reduced from 84.6%±7.5% to 10.7%±3.6% (p<0.01). In 5 patients with ZES implanted fully within the self-expanding carotid stent, duplex ultrasound follow-up (mean 17 months, range 6-36) revealed no evidence of restenosis or stent fracture/deformation. In the 2 other patients, the ZES had been implanted for distal edge ISS such that the ZES protruded beyond the original carotid stent. This protruding segment of the ZES demonstrated deformation/kinking in both; in one, this led to symptomatic stent occlusion. The use of coronary ZES in the treatment of recurrent carotid ISS is feasible and appears effective provided the ZES is placed entirely within the original stent. Placement of a coronary ZES outside the carotid stent scaffold should be avoided.

  2. Caracterización de la restenosis de stents coronarios convencionales y liberadores de medicamentos en pacientes incluidos en el registro DRug Eluting STent (DREST

    Directory of Open Access Journals (Sweden)

    Jorge A. Arroyave C., MD

    2012-05-01

    Conclusiones: las tasas de restenosis intrastent y las características relacionadas encontradas, son similares a lo publicado. La dislipidemia aparece como factor asociado significativo. La restenosis intrastent se manifestó como síndrome coronario agudo en 60% de los casos; no puede considerarse como un proceso benigno en esta población.

  3. Metabolic background determines the importance of NOS3 polymorphisms in restenosis after percutaneous coronary intervention: A study in patients with and without the metabolic syndrome

    NARCIS (Netherlands)

    Pons, D.; Monraats, P.S.; Zwinderman, A.H.; de Maat, M.P.M.; Doevendans, P.A.F.M.; de Winter, R.J.; Tio, R.A.; Waltenberger, J.; Jukema, J.W.

    2009-01-01

    Variation in the NOS3 gene has been related to the development of restenosis. The Glu298Asp polymorphism has previously been investigated for its effect on NO levels and the development of restenosis. However, the variability of findings gave rise to the hypothesis that the functional significance

  4. Photodynamic therapy of atherosclerosis and restenosis: a potentially exciting new treatment method

    Science.gov (United States)

    Vincent, G. Michael

    1994-07-01

    Photodynamic therapy (PDT) is the result of an interaction between light and a photoactive drug. The interaction produces cytotoxic oxygen radicals and radicals and microvascular collapse, resulting in tissue death. A number of photoactive drugs have been shown to accumulate in greater concentration in atherosclerotic plaque than in normal arterial wall and are potentially useful for PDT. The newer generation agents are safe and have brief skin phototoxicity as the only significant side effect. PDT in several animal models of atherosclerosis has shown plaque removal without damage to the artery wall if appropriate light energy is used, with no perforation, and no distal embolization or obstruction. In one such study we found that PDT using Photofrin and 630 nm laser light reduced the mean percent stenosis of 12 stenoses in 8 pigs from 63% to 40%, and in 7/12 of the segments from 63% to 16%, whereas in 2 untreated control lesions the mean stenosis progressed from 60% to 85%. PDT requires several days for tissue destruction, and immediate luminal enlargement by an adjunct angioplasty intervention may be appropriate. Animal studies suggest that PDT also inhibits the intimal hyperplasia process which follows vascular injury, and PDT may inhibit restenosis following clinical coronary angioplasty. The enthusiasm for PDT of atherosclerosis, therefore, stems from three important potential advantages of the technique: the apparent selectivity and safety of the process, the potential for effective debulking of plaque and the possibility of reduction or inhibition or restenosis.

  5. Recruitable collateral blood flow index predicts coronary instent restenosis after percutaneous coronary intervention

    DEFF Research Database (Denmark)

    Jensen, Lisette Okkels; Thayssen, Per; Lassen, Jens Flensted

    2007-01-01

    AIMS: Collateral flow may influence long-term results after percutaneous coronary intervention (PCI) because of haemodynamic forces compete with the antegrade flow through the dilated lesion. The aim of the study was to assess the influence of recruitable collateral blood flow on restenosis......-derived collateral flow index (CFI) was determined as (P(w)-P(cvp))/(P(a)-P(cvp)), where P(w) represents coronary wedge pressure, P(cvp) central venous pressure, and P(a) mean aortic blood pressure. Both were measured during transient coronary occlusion by a balloon inflation of 30 s. Pre-interventional FFR (0.......65 +/- 0.20) correlated inversely with the CFI (0.18 +/- 0.11), r =- 0.356, P /=50% diameter stenosis) was seen in 29.1%. Compared to patients with poorly developed collaterals (CFI collaterals (CFI >/= 0...

  6. Two-dimensional fluorescence in-gel electrophoresis of coronary restenosis tissues in minipigs: increased adipocyte fatty acid binding protein induces reactive oxygen species-mediated growth and migration in smooth muscle cells.

    Science.gov (United States)

    Lu, Lin; Wang, Ya Nan; Sun, Wei Hua; Liu, Zhu Hui; Zhang, Qi; Pu, Li Jin; Yang, Ke; Wang, Ling Jie; Zhu, Zhen Bin; Meng, Hua; Yang, Ping; Du, Run; Chen, Qiu Jing; Wang, Li Shun; Yu, Hong; Shen, Wei Feng

    2013-03-01

    We aimed to uncover the protein changes of coronary artery in-stent restenosis (ISR) tissue in minipigs with and without streptozotocin-induced diabetes mellitus by quantitative 2-dimensional fluorescence in-gel electrophoresis (2D-DIGE), and to investigate the influences of crucial proteins identified, particularly adipocyte fatty acid binding protein (AFABP), in human arterial smooth muscle cells. Sirolimus-eluting stents were implanted in the coronary arteries of 15 diabetic and 26 nondiabetic minipigs, and angiography was repeated after 6 months. The intima tissue of significant ISR and non-ISR segments in both diabetic and nondiabetic minipigs was analyzed by 2D-DIGE and MALDI-TOF/TOF mass spectrometry. AFABP level was significantly increased in ISR tissue than in non-ISR tissue in both diabetic and nondiabetic minipigs, with level being higher in diabetic ISR than in nondiabetic ISR tissue. In human arterial smooth muscle cells, overexpression of AFABP significantly altered phenotype and promoted growth and migration, with effects more prominent in high-glucose than in low-glucose medium, whereas AFABP knockdown inhibited these effects. AFABP overexpression increased reactive oxygen species production by upregulating the expression of NADPH oxidase subunits Nox1, Nox4, and P22 through multiple pathways, with elevation of downstream gene cyclin D1, matrix metalloproteinase-2, and monocyte chemoattractant protein-1. However, AFABP-induced effects were inhibited by diphenyleneiodonium, pathway inhibitors, and small interfering RNA. In addition, the supernatant from AFABP-expressing human arterial smooth muscle cells and recombinant AFABP also promoted cellular growth and migration. This study has demonstrated that AFABP is significantly increased in coronary artery ISR segments of both diabetic and nondiabetic minipigs. Increased AFABP expression and secretory AFABP of human arterial smooth muscle cells promote growth and migration via reactive oxygen species

  7. The sirolimus-eluting Cypher Select coronary stent for the treatment of bare-metal and drug-eluting stent restenosis: insights from the e-SELECT (Multicenter Post-Market Surveillance) registry.

    Science.gov (United States)

    Abizaid, Alexandre; Costa, J Ribamar; Banning, Adrian; Bartorelli, Antonio L; Dzavik, Vladimir; Ellis, Stephen; Gao, Runlin; Holmes, David R; Jeong, Muyng Ho; Legrand, Victor; Neumann, Franz-Josef; Nyakern, Maria; Orlick, Amy; Spaulding, Christian; Worthley, Stephen; Urban, Philip M

    2012-01-01

    This study sought to compare the 1-year safety and efficacy of Cypher Select or Cypher Select Plus (Cordis Corporation, Bridgewater, New Jersey) sirolimus-eluting stents (SES) with the treatment of bare-metal stents (BMS) and drug-eluting stent (DES) in-stent restenosis (ISR) in nonselected, real-world patients. There is paucity of consistent data on DES for the treatment of ISR, especially, DES ISR. The e-SELECT (Multicenter Post-Market Surveillance) registry is a Web-based, multicenter and international registry encompassing virtually all subsets of patients and lesions treated with at least 1 SES during the period from 2006 to 2008. We enrolled in this pre-specified subanalysis all patients with at least 1 clinically relevant BMS or DES ISR treated with SES. Primary endpoint was major adverse cardiac events and stent thrombosis rate at 1 year. Of 15,147 patients enrolled, 1,590 (10.5%) presented at least 1 ISR (BMS group, n = 1,235, DES group, n = 355). Patients with DES ISR had higher incidence of diabetes (39.4% vs. 26.9%, p target lesion revascularization and definite/probable late stent thrombosis were higher in patients with DES ISR (6.9% vs. 3.1%, p = 0.003, and 1.8% vs. 0.5%, p = 0.04, respectively). Use of SES for either BMS or DES ISR treatment is safe and associated with low target lesion revascularization recurrence and no apparent safety concern. Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  8. Impact of 6-month angiographic restenosis inside bare-metal stents on long-term clinical outcome in patients with coronary artery disease

    International Nuclear Information System (INIS)

    Chen Yunglung; Chen Miencheng; Wu Chiungjen

    2007-01-01

    This study enrolled 536 patients who underwent successful coronary stenting with bare-metal stents and 6-month angiographic follow-up examinations between 1998 and 2000. Baseline characteristics and angiographic and procedural parameters for these patients were obtained. Primary endpoints were all-cause mortality and nonfatal myocardial infarction. Patients were assigned to instent restenosis or non-instent restenosis groups based on 6-month angiographic follow-up results. Restenosis inside a bare-metal stent was defined as more than 50% stenosis at the intervention site. In total, 178 (33.2%) patients had restenosis inside bare-metal stents, while 358 (66.8%) patients were without. At mean follow-up of 56.8±20.3 months, 36 (6.7%) patients had a primary endpoint event while 500 (93.3%) patients had no primary endpoint event. Survival rates for patients free from primary endpoints in the instent restenosis and non-instent restenosis groups were 96.0 versus 99.4% at 1 year and 89.8% versus 94.8% at 5 years, respectively (P=0.0033). Survival rates for patients free of all-cause mortality in the instent restenosis and non-instent restenosis groups were 96.0% versus 99.4% at 1 year and 91.6% versus 96.3% at 5 years, respectively (P=0.0079). Multivariate Cox regression analysis showed that restenosis inside bare-metal stents was an independent predictor of primary endpoint events (odds ratio: 2.053; 95% CI: 1.048-4.022; P=0.036) and was a predictor of total mortality with borderline significance (odds ratio: 2.036; 95% CI: 0.936-4.431; P=0.073). In conclusion, in this study, restenosis inside bare-metal stents at 6-month angiographic follow-up was an independent predictor of long-term outcome-all-cause mortality and nonfatal myocardial infarction. Thus, this study provides clinical evidence that patients with restenosis inside bare-metal stents at 6-month angiographic follow-up likely warrant aggressive follow-up. (author)

  9. High Residual Collagen-Induced Platelet Reactivity Predicts Development of Restenosis in the Superficial Femoral Artery After Percutaneous Transluminal Angioplasty in Claudicant Patients

    Energy Technology Data Exchange (ETDEWEB)

    Gary, Thomas, E-mail: thomas.gary@medunigraz.at [Medical University of Graz, Division of Angiology, Department of Internal Medicine (Austria); Prüller, Florian, E-mail: florian.prueller@klinikum-graz.at; Raggam, Reinhard, E-mail: reinhard.raggam@klinikum-graz.at [Medical University of Graz, Clinical Institute of Medical and Chemical Laboratory Diagnostics (Austria); Mahla, Elisabeth, E-mail: elisabeth.mahla@medunigraz.at [Medical University of Graz, Department of Anesthesiology and Intensive Care Medicine (Austria); Eller, Philipp, E-mail: philipp.eller@medunigraz.at; Hafner, Franz, E-mail: franz.hafner@klinikum-graz.at; Brodmann, Marianne, E-mail: marianne.brodmann@medunigraz.at [Medical University of Graz, Division of Angiology, Department of Internal Medicine (Austria)

    2016-02-15

    PurposeAlthough platelet reactivity is routinely inhibited with aspirin after percutaneous angioplasty (PTA) in peripheral arteries, the restenosis rate in the superficial femoral artery (SFA) is high. Interaction of activated platelets and the endothelium in the region of intervention could be one reason for this as collagen in the subendothelium activates platelets.Materials and MethodsA prospective study evaluating on-site platelet reactivity during PTA and its influence on the development of restenosis with a total of 30 patients scheduled for PTA of the SFA. Arterial blood was taken from the PTA site after SFA; platelet function was evaluated with light transmission aggregometry. After 3, 6, 12, and 24 months, duplex sonography was performed and the restenosis rate evaluated.ResultsEight out of 30 patients developed a hemodynamically relevant restenosis (>50 % lumen narrowing) in the PTA region during the 24-month follow-up period. High residual collagen-induced platelet reactivity defined as AUC >30 was a significant predictor for the development of restenosis [adjusted odds ratio 11.8 (9.4, 14.2); P = .04].ConclusionsHigh residual collagen-induced platelet reactivity at the interventional site predicts development of restenosis after PTA of the SFA. Platelet function testing may be useful for identifying patients at risk.

  10. High Residual Collagen-Induced Platelet Reactivity Predicts Development of Restenosis in the Superficial Femoral Artery After Percutaneous Transluminal Angioplasty in Claudicant Patients.

    Science.gov (United States)

    Gary, Thomas; Prüller, Florian; Raggam, Reinhard; Mahla, Elisabeth; Eller, Philipp; Hafner, Franz; Brodmann, Marianne

    2016-02-01

    Although platelet reactivity is routinely inhibited with aspirin after percutaneous angioplasty (PTA) in peripheral arteries, the restenosis rate in the superficial femoral artery (SFA) is high. Interaction of activated platelets and the endothelium in the region of intervention could be one reason for this as collagen in the subendothelium activates platelets. A prospective study evaluating on-site platelet reactivity during PTA and its influence on the development of restenosis with a total of 30 patients scheduled for PTA of the SFA. Arterial blood was taken from the PTA site after SFA; platelet function was evaluated with light transmission aggregometry. After 3, 6, 12, and 24 months, duplex sonography was performed and the restenosis rate evaluated. Eight out of 30 patients developed a hemodynamically relevant restenosis (>50 % lumen narrowing) in the PTA region during the 24-month follow-up period. High residual collagen-induced platelet reactivity defined as AUC >30 was a significant predictor for the development of restenosis [adjusted odds ratio 11.8 (9.4, 14.2); P = .04]. High residual collagen-induced platelet reactivity at the interventional site predicts development of restenosis after PTA of the SFA. Platelet function testing may be useful for identifying patients at risk.

  11. Incidence, Clinical Presentation, and Predictors of Clinical Restenosis in Coronary Bioresorbable Scaffolds.

    Science.gov (United States)

    Polimeni, Alberto; Weissner, Melissa; Schochlow, Katharina; Ullrich, Helen; Indolfi, Ciro; Dijkstra, Jouke; Anadol, Remzi; Münzel, Thomas; Gori, Tommaso

    2017-09-25

    The aim of this study was to describe the incidence and clinical characteristics, including intracoronary imaging features, of clinical restenosis in bioresorbable coronary scaffolds (BRS). Further, the authors searched for clinical and procedural predictors of scaffold restenosis (ScR) and report on the clinical outcomes after treatment of ScR in a cohort of consecutive all-comer patients. Data from randomized controlled trials demonstrate a higher rate of target lesion failure in patients treated with BRS as compared with those treated with metal drug-eluting stents. Although in-scaffold thrombosis has been thoroughly investigated, there are little data available on the incidence and characteristics of ScR. A total of 657 consecutive patients (age 63 ± 12 years, 79% men, 21% diabetics, 67% acute coronary syndrome) who received a total of 883 BRS for the treatment of coronary artery stenoses between May 2012 and January 2015 were enrolled in a retrospective registry. During the median follow-up of 1,076 days (interquartile range: 762 to 1,206 days), a total of 49 cases of ScR were found in 41 patients (Kaplan-Meier incidence: 2.4%, 6.0%, and 9.0% at 12-, 24-, and 36-month follow-up, respectively). ScR presented as stable angina or as incidental finding in 73% of the cases. The angiographic pattern was complex (type II to IV) in 55% of the ScR lesions. The neointima was homogeneous with high signal intensity in all but 3 cases at optical coherence tomography. Prior revascularization (hazard ratio [HR]: 2.7; 95% confidence interval [CI]: 1.5 to 5.1; p = 0.002), diabetes (HR: 2.9; 95%CI: 1.5 to 5.4; p = 0.001), lesion types B2 or C (HR: 2.8; 95% CI: 1.5 to 5.4; p = 0.002), and implantation technique (HR: 0.3; 95% CI: 0.1 to 0.6; p = 0.001) emerged as independent predictors of ScR. Oversizing (HR: 6.29; 95% CI: 2.4 to 16.4), undersizing (HR: 5.15; 95% CI: 1.99 to 13.30), and a residual stenosis >27% (HR: 8.9; 95% CI: 3.6 to 21.8) were associated with an

  12. Fibrocellular tissue responses to endovascular and external beam irradiation in the porcine model of restenosis

    International Nuclear Information System (INIS)

    Marijianowski, Monique M.H.; Crocker, Ian R.; Styles, Terry; Forestner, Donna M.; Waksman, Ron; Cipolla, Gustavo D.; King, Spencer B.; Robinson, Keith A.

    1999-01-01

    Purpose: Endovascular radiation has reduced postangioplasty restenosis in preclinical and early clinical studies. External radiation treatment may have advantages over endovascular therapy. We examined vascular and perivascular tissue responses to endovascular and external irradiation in pig coronary arteries. Methods and Materials: Ninety-one animals received endovascular or external radiation following balloon injury and were sacrificed at 14, 30, or 180 days. Injured segments of coronary vessels including perivascular and myocardial tissues were evaluated with histochemistry. Results: Endovascular radiation was associated with delayed arterial wound healing as late as 6 months, evidenced by paucity of smooth muscle α-actin in neointimal cells compared to control. External treatment was associated with increased collagen in neointima and adventitia, and focal interstitial necrosis in adjacent myocardium. Conclusions: These investigations showed whole-heart 14 Gy external radiation treatment following coronary injury exacerbated certain aspects of arterial healing. In addition focal myocardial necrosis and fibrosis was observed following external but not endovascular irradiation. Endovascular radiation has some advantages over external irradiation; however the persistence of a synthetic smooth muscle cell phenotype in the neointima at 6 months suggests ionizing radiation in general may have profound effects on vessel architecture over the long term

  13. In-stent thrombosis when switching ticagrelor to clopidogrel after percutaneous coronary intervention.

    Science.gov (United States)

    Brice, Aaron E; Hernandez, Gabriel A; Sanchez, Mariluz; Haynick, Marshall; Mendoza, Cesar E

    2017-05-01

    Dual antiplatelet therapy with aspirin and a P2Y12 receptor blocker has been proven to reduce subsequent cardiovascular events and in-stent thrombosis in patients undergoing percutaneous coronary intervention. Newer P2Y12 antagonists with faster onset and greater inhibition of platelet activity have improved cardiovascular outcomes but have created uncertainty with the appropriate dosing when switching between agents. Currently, there are no evidence-based guidelines to aid clinicians when switching between P2Y12 receptor blockers. Here we describe two patients that developed in-stent thrombosis when switching from ticagrelor to clopidogrel using a 300 mg clopidogrel loading dose. Both patients presented with ST elevation myocardial infarction and underwent stent placement but then developed in-stent thrombosis 48 hours after switching from ticagrelor to clopidogrel. These cases illustrate the severe consequences of suboptimal platelet inhibition and the need for prospective trials thoroughly powered to assess clinical outcomes in order to determine the most appropriate strategy when switching from ticagrelor to clopidogrel.

  14. A combined strategy to reduce restenosis for vascular tissue engineering applications.

    Science.gov (United States)

    Patel, Hemang J; Su, Shih-Horng; Patterson, Cam; Nguyen, Kytai T

    2006-01-01

    Biodegradable polymers including poly(l-lactic acid) (PLLA) have been used to develop cardiovascular prostheses such as vascular grafts and stents. However, implant-associated thrombosis, inflammation, and restenosis are still major obstacles for the utility of these devices. The lack of an endothelial cell (EC) lining (endothelialization) on the implants and the responses of the immune systems toward the implants have been associated with these complications. In our research strategy, we have combined the drug delivery principle with the strategies of tissue engineering, the controlled release of anti-inflammation drugs and enhanced endothelialization, to reduce the implant-associated adverse responses. We first integrated curcumin, an anti-inflammatory drug and anti-smooth muscle cell (SMC) proliferative drug, with PLLA. This curcumin-loaded PLLA material was then modified using adsorptive coating of adhesive proteins such as fibronectin, collagen-I, vitronectin, laminin, and matrigel to improve the endothelial cell (EC) adhesion and proliferation, and ECs were seeded on top of these modified surfaces. Our results showed steady drug release kinetics over the period of 50 days from curcumin-loaded PLLA materials. Additionally, integration of curcumin in PLLA increased the roughness of the scaffold at the nanometric scale using an atomic force microscopic analysis. Moreover, coating with fibronectin on curcumin-loaded PLLA surfaces gave the highest EC adhesion and proliferation compared to other adhesive proteins using PicoGreen DNA assays. The ability of our strategy to release the curcumin for producing anti-inflammation and anti-proliferation responses and to improve EC adhesion and growth after EC seeding suggests this strategy may reduce implant-associated adverse responses and be a better approach for vascular tissue engineering applications.

  15. Sulforaphane inhibits restenosis by suppressing inflammation and the proliferation of vascular smooth muscle cells.

    Science.gov (United States)

    Kwon, Jin-Sook; Joung, Hosouk; Kim, Yong Sook; Shim, Young-Sun; Ahn, Youngkeun; Jeong, Myung Ho; Kee, Hae Jin

    2012-11-01

    Sulforaphane, a naturally occurring organosulfur compound in broccoli, has chemopreventive properties in cancer. However, the effects of sulforaphane in vascular diseases have not been examined. We therefore aimed to investigate the effects of sulforaphane on vascular smooth muscle cell (VSMC) proliferation and neointimal formation and the related mechanisms. The expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) was examined in VSMCs. The nuclear translocation of nuclear factor-κB (NF-κB) and GATA6 expression was examined in VSMCs and in a carotid artery injury model by Western blot and immunohistochemistry. We also investigated whether local delivery of sulforaphane affected neointimal formation. Sulforaphane inhibited the mRNA and protein expression of VCAM-1 induced by tumor necrosis factor (TNF)-α in VSMCs. Treatment of VSMCs with sulforaphane blocked TNF-α-induced IκBα degradation and NF-κB p65 and GATA6 expression. Furthermore, NF-κB p65 and GATA6 expression were reduced in sulforaphane-treated carotid injury sections. Notably, binding of GATA6 to the VCAM-1 promoter was dramatically reduced by sulforaphane. The MTT, BrdU incorporation, and in vitro scratch assays revealed that the proliferation and migration of VSMCs were reduced by sulforaphane. Furthermore, local administration of sulforaphane significantly reduced neointima formation 14 days after vascular injury in rats. Our results indicate that sulforaphane inhibits neointima formation via targeting of adhesion molecules through the suppression of NF-κB/GATA6. Furthermore, sulforaphane regulates migration and proliferation in VSMCs. Sulforaphane may be a potential therapeutic agent for preventing restenosis after vascular injury. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  16. Using oxidized low-density lipoprotein autoantibodies to predict restenosis after balloon angioplasty in patients with acute myocardial infarction.

    Directory of Open Access Journals (Sweden)

    Ching-Hui Huang

    Full Text Available OBJECTIVES: Oxidized low-density lipoproteins (oxLDL and oxidized low-density lipoprotein autoantibodies (OLAB have been detected in human plasma and atherosclerotic lesions. OLAB appear to play a role in the clearance of oxLDL from circulation. Higher levels of OLAB appear to be associated with a reduced risk of a wide range of cardiovascular diseases. We investigated the prognostic value of plasma oxLDL and OLAB in patients undergoing primary coronary balloon angioplasty for acute ST-elevation myocardial infarction (STEMI. METHODS: Plasma oxLDL and OLAB concentrations were measured in 56 patients with acute STEMI before primary angioplasty, and then 3 days, 7 days and 1 month after the acute event. Follow-up angiography was repeated 6 months later to detect the presence of restensosis (defined as >50% luminal diameter stenosis. The thrombolysis in myocardial infarction (TIMI risk score was calculated to determine the relationship between OLAB/oxLDL ratio and TIMI risk scores. RESULTS: Of the 56 patients, 18 (31% had angiographic evidence of restenosis. Plasma OLAB concentrations were significantly lower in the restenosis group before angioplasty (181±114 vs. 335±257 U/L, p = 0.003, and at day 3 (155±92 vs. 277±185 U/L, p<0.001 and day 7 (177±110 vs. 352±279 U/L, p<0.001 after the acute event. There was no difference in oxLDL concentration between the two groups. The ratio of OLAB/oxLDL positively correlated with TIMI risk scores before angioplasty (p for trend analysis, p = 0.004, at day 3 (p = 0.008 and day 7 (p<0.001 after STEMI. SIGNIFICANCE: A relative deficit of OLAB, and hence likely impaired clearance of oxLDL, is associated with the risk of arterial restenosis after primary angioplasty for acute STEMI.

  17. Matrix Metalloproteinases 2 and 3 Gene Polymorphisms and the Risk of Target Vessel Revascularization after Percutaneous Coronary Intervention: Is There Still Room for Determining Genetic Variation of MMPs for Assessment of an Increased Risk of Restenosis?

    Directory of Open Access Journals (Sweden)

    J.J.W. Verschuren

    2010-01-01

    Full Text Available Objective: Mixed results have been reported of matrix metalloproteinases (MMP and their association with restenosis after percutaneous coronary intervention (PCI. The current study examines whether multiple single nucleotide polymorphisms (SNPs, covering the full genomic region of MMP2 and MMP3, were associated with restenosis in the GENDER study population.

  18. Detection of restenosis after successful coronary angioplasty: Improved clinical decision making with use of a logistic model combining procedural and follow-up variables

    International Nuclear Information System (INIS)

    Renkin, J.; Melin, J.; Robert, A.; Richelle, F.; Bachy, J.L.; Col, J.; Detry, J.M.; Wijns, W.

    1990-01-01

    A prospective study of 111 patients who underwent repeat coronary angiography and exercise thallium-201 scintigraphy 6 +/- 2 months after complete revascularization by percutaneous transluminal coronary angioplasty was performed to assess whether clinical, procedure-related and postangioplasty exercise variables yield independent information for the prediction of angiographic restenosis after angioplasty. Complete revascularization was defined as successful angioplasty of one or more vessels that resulted in no residual coronary lesion with greater than 50% diameter stenosis. Restenosis was defined as a residual stenosis at the time of repeat angiography of greater than 50% of luminal diameter. Restenosis occurred in 40% of the patients. The 111 patients were randomly subdivided into a learning group (n = 84) and a testing group (n = 27). A logistic discriminant analysis was performed in the learning group and the logistic model was used to estimate a logistic probability of restenosis. This probability of restenosis was validated in the testing group. In the learning group of 84 patients univariate analysis of 39 factors revealed 8 factors related to restenosis: recurrence of angina (p less than 0.0001), postangioplasty abnormal finding on exercise thallium-201 scintigram (p less than 0.0001), exercise thallium-201 scintigram score (p less than 0.0001), difference between exercise and rest ST segment depression (p less than 0.001), postangioplasty exercise ST segment depression (p less than 0.001), absolute postangioplasty stenosis diameter (p less than 0.003), postangioplasty exercise work load (p less than 0.03) and postangioplasty exercise heart rate (p less than 0.05)

  19. The Relationships between Polymorphisms in Genes Encoding the Growth Factors TGF-β1, PDGFB, EGF, bFGF and VEGF-A and the Restenosis Process in Patients with Stable Coronary Artery Disease Treated with Bare Metal Stent.

    Directory of Open Access Journals (Sweden)

    Tadeusz Osadnik

    Full Text Available Neointima forming after stent implantation consists of vascular smooth muscle cells (VSMCs in 90%. Growth factors TGF-β1, PDGFB, EGF, bFGF and VEGF-A play an important role in VSMC proliferation and migration to the tunica intima after arterial wall injury. The aim of this paper was an analysis of functional polymorphisms in genes encoding TGF-β1, PDGFB, EGF, bFGF and VEGF-A in relation to in-stent restenosis (ISR.265 patients with a stable coronary artery disease (SCAD hospitalized in our center in the years 2007-2011 were included in the study. All patients underwent stent implantation at admission to the hospital and had another coronary angiography performed due to recurrence of the ailments or a positive result of the test assessing the coronary flow reserve. Angiographically significant ISR was defined as stenosis >50% in the stented coronary artery segment. The patients were divided into two groups-with angiographically significant ISR (n = 53 and without significant ISR (n = 212. Additionally, the assessment of late lumen loss (LLL in vessel was performed. EGF rs4444903 polymorphism was genotyped using the PCR-RFLP method whilst rs1800470 (TGFB1, rs2285094 (PDGFB rs308395 (bFGF and rs699947 (VEGF-A were determined using the TaqMan method.Angiographically significant ISR was significantly less frequently observed in the group of patients with the A/A genotype of rs1800470 polymorphism (TGFB1 versus patients with A/G and G/G genotypes. In the multivariable analysis, LLL was significantly lower in patients with the A/A genotype of rs1800470 (TGFB1 versus those with the A/G and G/G genotypes and higher in patients with the A/A genotype of the VEGF-A polymorphism versus the A/C and C/C genotypes. The C/C genotype of rs2285094 (PDGFB was associated with greater LLL compared to C/T heterozygotes and T/T homozygotes.The polymorphisms rs1800470, rs2285094 and rs6999447 of the TGFB1, PDGFB and VEGF-A genes, respectively, are associated with LLL

  20. Use of Rhenium-188 Liquid-Filled Balloons for Inhibition of Coronary Restenosis After PTCA - A New Opportunity for Nuclear Medicine

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, F.F., Jr.; Spencer, R.H.; Stabin, M.

    1999-05-13

    Although the use of ionizing radiation for the treatment of benign lesions such as keloids has been available for nearly one hundred years, only recently have the cost effective benefits of such technology for the inhibition of arterial restenosis following controlled vessel damage from balloon angioplasty been fully realized. In particular, the use of balloons filled with solutions of beta-emitting radioisotopes for vessel irradiation provide the benefit of uniform vessel irradiation. Use of such contained ("unsealed") sources is expected to represent a new opportunity for nuclear medicine physicians working in conjunction with interventional cardiologists to provide this new approach for restenosis therapy.

  1. Restenosis in coronary bare metal stents. Importance of time to follow-up: a comparison of coronary angiograms 6 months and 4 years after implantation

    DEFF Research Database (Denmark)

    Jørgensen, Erik; Helqvist, Steffen; Kløvgaard, Lene

    2008-01-01

    Objectives. Angiographic late lumen loss measured 6 to 9 month after bare metal stent implantation in the coronary arteries is a validated restenosis parameter. Design. We performed a second angiographic follow-up after 4 years in event free survivors from the DANSTENT trial cohort. Results......-sectional vessel area and a 39% reduction of the binary restenosis rate over time. Conclusions. Instent late lumen loss in bare metal stents decreases spontaneously over time. Maturation of early hyperplastic tissue reaction after stent implantation with subsequent thinning of fibrotic tissue might explain...

  2. Increased Plasma Cathepsin S at the Time of Percutaneous Transluminal Angioplasty is Associated with 6-Months’ Restenosis of the Femoropopliteal Artery

    Directory of Open Access Journals (Sweden)

    Mijovski Mojca Bozic

    2018-01-01

    Full Text Available Background: We tested the hypothesis that increased levels of cathepsin S and decreased levels of cystatin C in plasma at the time of percutaneous transluminal angioplasty (PTA are associated with the occurrence of 6-months’ restenosis of the femoropopliteal artery (FPA. Methods: 20 patients with restenosis and 24 matched patients with patent FPA after a 6-months follow-up were in - cluded in this study. They all exhibited disabling claudication or critical limb ischemia and had undergone technically successful PTA. They were all receiving statins and ACE in hi - bitors (or angiotensin II receptor antagonist before the PTA and the therapy did not change throughout the observational period. Plasma concentrations of C-reactive protein were < 10 mg/L and of creatinine within the reference range at the time of the PTA. Plasma concentration and activity of cathepsin S, together with its potent inhibitor cystatin C, were measured the day before and the day after the PTA. Results: The increased plasma concentration and activity of cathepsin S at the time of PTA was associated with the occurrence of 6-months’ restenosis of FPA, independently of established risk factors (lesion complexity, infrapopliteal run-off vessels, type of PTA, age, gender, smoking, diabetes, lipids and of cystatin C. Plasma cystatin C concentration was not associated with restenosis and did not correlate with cathepsin S activity and concentration in the plasma. Conclusion: Increased level of plasma cathepsin S at the time of PTA is associated with 6-months’ restenosis of PTA, independently of established risk factors.

  3. Monocyte to HDL ratio in prediction of BMS restenosis in subjects with stable and unstable angina pectoris.

    Science.gov (United States)

    Tok, Derya; Turak, Osman; Yayla, Çağrı; Ozcan, Fırat; Tok, Duran; Çağlı, Kumral

    2016-08-01

    This study aims to assess the predictive role of the preprocedural circulating monocyte to high-density lipoprotein (HDL) cholesterol ratio (MHR) on the occurrence of stent restenosis (SR) in patients with stable and unstable angina pectoris undergoing successful bare-metal stenting (BMS). Between February 2008 and June 2014, a total of 831 patients with stable and unstable angina pectoris who underwent successful BMS were retrospectively analyzed. Demographic and clinical characteristics of the patients were recorded. Left ventricular ejection fraction and laboratory data were also noted. In the receiver operating characteristics curve analysis, MHR >14 had 71% sensitivity and 69% specificity in predicting SR. Our study results show that preprocedural MHR is an independent predictor of SR in this patient population.

  4. Preclinical study investigating the potential of low-dose-rate brachytherapy with32P stents for the prevention of restenosis of paranasal neo-ostia.

    Science.gov (United States)

    Oestreicher, Elmar; Bartsch, Harald; Mayr, Doris; Schubert, Mario; Weber, Barbara; Kneschaurek, Peter; Assmann, Walter; Sroka, Ronald; Betz, Christian Stephan

    Ostial restenosis is a common cause of failures in paranasal sinus surgery. The aim of the current study was to investigate the use of low-dose-rate brachytherapy to prevent neo-ostial restenosis in an animal model. In 14 rabbits, maxillary neo-ostia were created and measured. One side each was stented with a regular silicone stent, the other side was either not stented (n = 7) or stented with a phosphorous-32 implanted stent depositing a low-dose radiation of 15 Gy (n = 7) within 1 week, after which all stents were removed. After a period of additional 12 weeks of recovery, the animals were sacrificed, the neo-ostia were again measured, and the areas and histopathologic changes compared in between the groups. After 15-Gy stenting, the mean ostial areas were even slightly enlarged by 5.1% compared to the area at stent removal, whereas a significant reduction in area, indicating a process of restenosis, by 56.1% or 54.0% was seen in the control groups with no stent and normal stent, respectively. Furthermore, no indication for adverse histopathologic radiation effects was seen in the 15-Gy group. Low-dose-rate brachytherapy with phosphorous-32 doped silicone stents showed promising results in the prevention of neo-ostium restenosis in this proof-of-concept study, indicating that further preclinical and clinical testing may be warranted. Copyright © 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  5. Comparison of the very long term (>1 year) outcomes of drug-eluting stents for the treatment of bare-metal and drug-eluting stent restenosis.

    Science.gov (United States)

    Ribamar Costa, Jose; Sousa, Amanda G M R; Moreira, Adriana; Alves da Costa, Ricardo; Cano, Manuel N; Maldonado, Galo; Campos Neto, Cantídio; Jardim, César; Pavanello, Ricardo; Sousa, Jose Eduardo

    2009-09-01

    Drug-eluting stents (DES) have become the first choice to treat BMS restenosis (ISR), replacing brachytherapy and all other available percutaneous approaches. Although markedly reduced, DES ISR still occurs and has been frequently treated with another DES, despite the lack of robust data supporting the safety and efficacy of this approach. We sought to compare the long term clinical outcomes of patients with BMS and DES ISR treated with another DES deployment. Between May 2002 and January 2008 a total of 158 patients with BMS restenosis and 58 patients with DES restenosis were treated with a DES and enrolled in this registry. Primary endpoint included the cumulative occurrence of major adverse cardiac events (MACE=cardiac death, myocardial infarction and target-vessel revascularisation) and stent thrombosis. Baseline clinical aspects did not significantly differ between the groups. There was a trend toward a higher incidence of DM in the DES cohort (36.1% vs. 32.9%, p=0.1). Mean time between first procedure and restenosis was significant longer in the DES population (178+/-61 days vs. 140+/-38 days, p=0.02). At the end of the follow-up period, 92.6% of the patients with BMS-ISR and 86.3% of those with DES-ISR were free of MACE (p<0.001). Patients with DES ISR had significant more recurrence of ISR but equivalent rates of cardiac death, MI and stent thrombosis. Percutaneous treatment of BMS or DES ISR with the implant of a DES represents a simple and safe approach with sustained long term results. However, the relatively high rate of ISR recurrence among patients with prior DES ISR demand the developing of more effective strategies for that subset of individuals.

  6. Diffuse scattering

    Energy Technology Data Exchange (ETDEWEB)

    Kostorz, G. [Eidgenoessische Technische Hochschule, Angewandte Physik, Zurich (Switzerland)

    1996-12-31

    While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs.

  7. Delivery of TFPI-2 using SonoVue and adenovirus results in the suppression of thrombosis and arterial re-stenosis.

    Science.gov (United States)

    Wang, Yuxue; Zhou, Jie; Zhang, Yanrong; Wang, Ximing; Chen, Juan

    2010-09-01

    Genes could be used to treat atherosclerosis. The key problem is how to target a gene through the walls of arteries in free-flowing blood. TFPI-2 has been shown to suppress thrombosis and arterial re-stenosis, which indicates its potential function in gene therapy for atherosclerosis. The microbubble ultrasound contrast agent is widely applied in diagnostic imaging, and could be used for transferring genes into arteries. By transfecting TFPI-2 into arteries using SonoVue (a kind of microbubble ultrasound contrast agent), we identified TFPI-2 as an available factor for inhibiting the proliferation of vascular endothelial cells in vivo. Compared with adenovirus, SonoVue showed similar gene transfection efficiency, but the latter showed stronger inhibition of thrombosis and arterial re-stenosis with a high expression of TFPI-2 protein in vitro and in vivo. SonoVue was less damaging when transfecting genes into the arterial wall. These data indicate that transfecting human TFPI-2 into the arterial wall may suppress thrombosis and arterial re-stenosis, and reduce atherosclerosis.

  8. Relativistic diffusion.

    Science.gov (United States)

    Haba, Z

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  9. Beyond Oncogenesis: The Role of S-Phase Kinase-Associated Protein-2 (SKP2 In Vascular Restenosis

    Directory of Open Access Journals (Sweden)

    Yih-Jer Wu

    2008-12-01

    Full Text Available The clinical benefits of percutaneous coronary intervention, the most prevalent procedure nowadays for the treatment of symptomatic coronary artery disease, are frequently offset by the occurrence of vascular restenosis. Although the introduction of drug-eluting stents has significantly reduced restenotic rates, the rare, but potentially fatal, delayed thrombosis remains a clinical threat. Further refinement of the drug-eluting stent based on a better understanding of cell cycle regulation between the vascular smooth muscle cell (VSMC and endothelial cell (EC is required. In this review, we discuss the role of S-phase kinase-associated protein-2 (Skp2, previously known as an oncoprotein, in the regulation of VSMC proliferation and its signaling axis. The currently available evidence suggests that the Rac1-Skp2-p27Kip1 signaling axis acts as a common final pathway for many factors that regulate VSMC proliferation, such as growth factors, extracellular matrices and cyclic nucleotides. Importantly, although EC proliferation is also shown to be regulated by the same axis, cAMP seems to regulate this axis differentially between VSMC and EC, rendering the underlying mechanism of this differential regulation a promising target for the development of a new generation of drug-eluting stent.

  10. Inhibition effect of tacrolimus and platelet-derived growth factor-BB on restenosis after vascular intimal injury.

    Science.gov (United States)

    Ma, Xu; Jiang, Chunyu; Li, Yuehua; Feng, Lishuai; Liu, Jingjing; Wang, Jianbo

    2017-09-01

    Excessive proliferation and migration of vascular smooth muscle cells(VSMCs) and delayed proliferation and migration of endothelial cells(ECs) were the main cause of restenosis after endovascular interventional therapy. Since tacrolimus has proved to be more sensitive to inhibiting VSMCs' proliferation,and platelet-derived growth factor-BB(PDGF-BB) benefitted ECs' and VSMCs' proliferation, this study was aimed to identify combined effect of tacrolimus and PDGF-BB, investigate any mechanisms underneath and demonstrate combined effect of two drugs in vivo. As the results showed we confirmed differential effect of PDGF-BB and tacrolimus on ECs and VSMCs. On the concentration level of 2-5μg/ml tacrolimus plus 10ng/ml PDGF-BB, combination of drugs could effectively promote ECs proliferation and migration, and meanwhile inhibit VSMCs proliferation and migration, and the inhibition of p-mTOR's expression within VSMCs played an important role in this differentiated effect. Raising concentration level of PDGF-BB would weaken inhibitory effect of tacrolimus on both kinds of cell. For injured intima, the mix solution of two drugs could promote intima healing and suppress excessive intimal hyperplasia. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  11. Diffusion bonding

    International Nuclear Information System (INIS)

    Anderson, R.C.

    1976-01-01

    A method is described for joining beryllium to beryllium by diffusion bonding. At least one surface portion of at least two beryllium pieces is coated with nickel. A coated surface portion is positioned in a contiguous relationship with another surface portion and subjected to an environment having an atmosphere at a pressure lower than ambient pressure. A force is applied on the beryllium pieces for causing the contiguous surface portions to abut against each other. The contiguous surface portions are heated to a maximum temperature less than the melting temperature of the beryllium, and the applied force is decreased while increasing the temperature after attaining a temperature substantially above room temperature. A portion of the applied force is maintained at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions

  12. Multipassage diffuser

    International Nuclear Information System (INIS)

    Lalis, A.; Rouviere, R.; Simon, G.

    1976-01-01

    A multipassage diffuser having 2p passages comprises a leak-tight cylindrical enclosure closed by a top cover and a bottom end-wall, parallel porous tubes which are rigidly assembled in sectors between tube plates and through which the gas mixture flows, the tube sectors being disposed at uniform intervals on the periphery of the enclosure. The top tube plates are rigidly fixed to an annular header having the shape of a half-torus and adapted to communicate with the tubes of the corresponding sector. Each passage is constituted by a plurality of juxtaposed sectors in which the mixture circulates in the same direction, the header being divided into p portions limited by radial partition-walls and each constituting two adjacent passages. The diffuser is provided beneath the bottom end-wall with p-1 leak-tight chambers each adapted to open into two different portions of the header, and with two collector-chambers each fitted with a nozzle for introducing the gas mixture and discharging the fraction of the undiffused mixture. By means of a central orifice formed in the bottom end-wall the enclosure communicates with a shaft for discharging the diffused fraction of the gas mixture

  13. Intraarterial 192Ir high-dose-rate brachytherapy for prophylaxis of restenosis after femoropopliteal percutaneous transluminal angioplasty: the prospective randomized Vienna-2-trial radiotherapy parameters and risk factors analysis

    International Nuclear Information System (INIS)

    Pokrajac, Boris; Poetter, Richard; Maca, Thomas; Fellner, Claudia; Mittlboeck, Martina; Ahmadi, Ramazanali; Seitz, Wolfgang; Minar, Erich

    2000-01-01

    Purpose: The aim of the Vienna-2-trial was to compare the restenosis rate of femoropopliteal arteries after percutaneous transluminal angioplasty (PTA) with or without intraarterial high-dose-rate (HDR) brachytherapy (BT) using an 192 Ir source. Materials and Methods: A prospective, randomized trial was conducted from 11/96 to 8/98. A total of 113 patients (63 men, 50 women), with a mean age of 71 years (range, 43-89 years) were included. Inclusion criteria were (1) claudication or critical limb ischemia, (2) de-novo stenosis of 5 cm or more, (3) restenosis after former PTA of any length, and (4) no stent implantation. Patients were randomized after successful PTA for BT vs. no further treatment. A well-balanced patient distribution was achieved for the criteria used for stratification, as there were 'de-novo stenosis vs. restenosis after former PTA', 'stenosis vs. occlusion', 'claudication vs. critical limb ischemia' and above these for 'diabetes vs. nondiabetes'. PTA length was not well balanced between the treatment arms: a PTA length of 4-10 cm was seen in 19 patients in the PTA alone group and in 11 patients in the PTA+BT group, whereas a PTA length of greater than10 cm was seen in 35 patients and 42 patients, respectively. A dose of 12 Gy was prescribed in 3-mm distance from the source axis. According to AAPM recommendations, the dose was 6.8 Gy in 5-mm distance (vessel radius + 2 mm). Primary endpoint of the study was femoropopliteal patency after 6 months. Results: PTA and additional BT were feasible and well tolerated by all 57 pts in this treatment arm. No acute, subacute, and late adverse side effects related to BT were seen after a mean follow up of 12 months (6-24 months) in 107 patients (PTA n = 54; PTA+ BT n = 53). Crude restenosis rate at 6 months was in the PTA arm 54% vs. 28% in the PTA + BT arm (χ 2 test; p 10 cm) showed significant decrease of the restenosis rate, if BT was added. Significant reduction was not achieved in diabetes patients

  14. Effects of abciximab on key pattern of human coronary restenosis in vitro: impact of the SI/MPL-ratio

    Directory of Open Access Journals (Sweden)

    Baur Regine

    2006-04-01

    Full Text Available Abstract Background The significant reduction of angiographic restenosis rates in the ISAR-SWEET study (intracoronary stenting and antithrombotic regimen: is abciximab a superior way to eliminate elevated thrombotic risk in diabetes raises the question of whether abciximab acts on clopidogrel-independent mechanisms in suppressing neointimal hyperplasia. The current study investigates the direct effect of abciximab on ICAM-1 expression, migration and proliferation. Methods ICAM-1: Part I of the study investigates in cytoflow studies the effect of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 μg/ml on TNF-α induced expression of intercellular adhesion molecule 1 (ICAM-1. Migration: Part II of the study explored the effect of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 μg/ml on migration of HCMSMC over a period of 24 h. Proliferation: Part III of the study investigated the effect of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 μg/ml on proliferation of HUVEC, HCAEC, and HCMSMC after an incubation period of 5 days. Results ICAM-1: In human venous endothelial cells (HUVEC, human coronary endothelial cells (HCAEC and human coronary medial smooth muscle cells (HCMSMC no inhibitory or stimulatory effect on expression of ICAM-1 was detected. Migration: After incubation of HCMSMC with abciximab in concentrations of 0.0002 – 2 μg/ml a stimulatory effect on cell migration was detected, statistical significance was achieved after incubation with 0.002 μg/ml (p 1. Conclusion Thus, the anti-restenotic effects of systemically administered abciximab reported in the ISAR-SWEET-study were not caused by a direct inhibitory effect on ICAM-1 expression, migration or proliferation.

  15. Re-examining minimal luminal diameter relocation and quantitative coronary angiography - Intravascular ultrasound correlations in stented saphenous vein grafts: Methodological insights from the randomised RRISC trial

    NARCIS (Netherlands)

    O. Semeraro (Oscar); P. Agostoni (Pierfrancesco); S. Verheye (Stefan); G.J.J. van Langenhove (Glenn); P.A. van den Heuvel (Paul); C. Convens (Carl); F. van den Branden (Frank); N. Bruining (Nico); P. Vermeersch (Paul)

    2009-01-01

    textabstractAims: Angiographic parameters (such as late luminal loss) are common endpoints in drug-eluting stent trials, but their correlation with the neointimal process and their reliability in predicting restenosis are debated. Methods and results: Using quantitative coronary angiography (QCA)

  16. The Impact of Blood Rheology on Drug Transport in Stented Arteries: Steady Simulations

    Science.gov (United States)

    Vijayaratnam, Pujith R. S.; O’Brien, Caroline C.; Reizes, John A.; Barber, Tracie J.; Edelman, Elazer R.

    2015-01-01

    Background and Methods It is important to ensure that blood flow is modelled accurately in numerical studies of arteries featuring drug-eluting stents due to the significant proportion of drug transport from the stent into the arterial wall which is flow-mediated. Modelling blood is complicated, however, by variations in blood rheological behaviour between individuals, blood’s complex near-wall behaviour, and the large number of rheological models which have been proposed. In this study, a series of steady-state computational fluid dynamics analyses were performed in which the traditional Newtonian model was compared against a range of non-Newtonian models. The impact of these rheological models was elucidated through comparisons of haemodynamic flow details and drug transport behaviour at various blood flow rates. Results Recirculation lengths were found to reduce by as much as 24% with the inclusion of a non-Newtonian rheological model. Another model possessing the viscosity and density of blood plasma was also implemented to account for near-wall red blood cell losses and yielded recirculation length increases of up to 59%. However, the deviation from the average drug concentration in the tissue obtained with the Newtonian model was observed to be less than 5% in all cases except one. Despite the small sensitivity to the effects of viscosity variations, the spatial distribution of drug matter in the tissue was found to be significantly affected by rheological model selection. Conclusions/Significance These results may be used to guide blood rheological model selection in future numerical studies. The clinical significance of these results is that they convey that the magnitude of drug uptake in stent-based drug delivery is relatively insensitive to individual variations in blood rheology. Furthermore, the finding that flow separation regions formed downstream of the stent struts diminish drug uptake may be of interest to device designers. PMID:26066041

  17. Asymptotic analysis of blood flow in stented arteries: time dependency and direct simulations***

    Directory of Open Access Journals (Sweden)

    Pichon Gostaf Kirill

    2010-12-01

    Full Text Available This work aims to extend in two distinct directions results recently obtained in [10]. In a first step we focus on the possible extension of our results to the time dependent case. Whereas in the second part some preliminary numerical simulations aim to give orders of magnitudes in terms of numerical costs of direct 3D simulations. We consider, in the first part, the time dependent rough problem for a simplified heat equation in a straight channel that mimics the axial velocity under an oscillating pressure gradient. We derive first order approximations with respect to ϵ, the size of the roughness. In order to understand the problem and set up correct boundary layer approximations, we perform a time periodic fourier analysis and check that no frequency can interact with the roughness. We show rigorously on this toy problem that the boundary layers remain stationary in time (independent on the frequency number. Finally we perform numerical tests validating our theoretical approach. In the second part, we determine actual limits, when running three-dimensional blood flow simulations of the non-homogenized stented arteries. We solve the stationary Stokes equations for an artery containing a saccular aneurysm. Consecutive levels of uniform mesh refinement, serve to relate spatial resolution, problem scale, and required computation time. Test computations are presented for femoral side aneurysm, where a simplified ten-wire stent model was placed across the aneurysm throat. We advocate the proposed stent homogenization model, by concluding that an actual computation power is not sufficient to run accurate, direct simulations of a pulsatile flow in stented vessels.

  18. Stent graft treatment for infra-inguinal arterial disease for either instent-restenosis and denovo lesions associated with very high rates of failure.

    Science.gov (United States)

    Golla, Maheswara S; Acharji, Subasit; Paul, Timir K; Madapathi, Praveena; Garcia, Lawrence A

    2017-12-07

    FDA approved the Gore Viabahn (WL Gore, Flagstaff, AZ, USA) stent for both femoro-popliteal arterial denovo and instent restenosis (ISRS) lesions. To date there is little data on Viabahn stent graft outcomes in ISRS arterial disease. Between 2007 and 2014 we identified 734 patients who underwent 1573 endovascular interventions in our institution for infra-inguinal revascularization. Among these, 48 patients had 143 Viabahn stents placed. Of these, 26 patients had 94 stents placed for ISRS and 22 patients had 49 stents placed for denovo lesions. The patients in the ISRS group were younger and more likely to have hypertension, hyperlipidemia, coronary artery disease, compared to the patients in the denovo group. Stents were placed principally for femoro-popliteal lesions, with mean length of 21 ± 12.5 cm (19.2 ± 14, ISRS vs. 22.1 ± 11, denovo; P = 0.2). Both groups had low primary patency rates during one year follow up (54% vs. 33%, OR = 2.3 (0.9-2.2). Target lesion revascularization (TLR) (57% vs. 27%, P ISRS group than in the denovo group. Amputation rate (17% vs. 31%, OR 0.7, CI = 0.2-1), cumulative blockage (defined as ISRS and thrombosis) (62% vs. 47%, P = 0.09, OR = 1.8, CI = 0.9-3.6), and Restenosis (40% vs. 31%, OR 1.5, CI = 0.7-3.2) were not statistically different between the two groups. Mean duration of follow-up was 12.8 ± 13 months. Stent graft treatment using the Gore Viabahn for denovo and ISRS in femoro-popliteal arterial obstructive disease have high restenosis and failure rates, of both stent patency and limb outcomes, which is consistent with existed literature. © 2017 Wiley Periodicals, Inc.

  19. [Coronary angioplasty in patients with restenosis. Characterization of clinical and angiographic profiles, hospital clinical course, and implications for the selection of patients].

    Science.gov (United States)

    Nunes, G L; Centemero, M P; Feres, F; Pinto, I M; Chaves, A; Mattos, L A; Tanajura, L F; Maldonado, G; Cano, M; Sousa, A G

    1995-09-01

    To define the clinical and angiographic profile of patients undergoing to a 2nd or a 3rd coronary angioplaty (PTCA) for the treatment of restenosis, and assess the safety and efficacy of redilatation. Patients submitted to PTCA for a 1st (1stRE) or a 2nd (2ndRE) restenosis, from Jan/1980 through Dec/1993, were retrospectively identified, and compared to those undergoing to PTCA for de novo lesions (DN). A total of 5,736 underwent to dilatation of primary lesions, 610 of a 1stRE, and 64 of a 2ndRE. Patients with restenotic lesions had a higher prevalence of diabetes, smoking, history of prior infarction (1stRE e 2ndRE) and hyperlipidemia (2ndRE) as compared with primary lesions (p < 0.05). Besides patients with a 2ndRE had a higher incidence of left ventricular dysfunction, as compared to those with DN or a 1stRE (31.3% with EF < 45% in group 2ndRE, vs 19.8% and 23.1% in groups 1stRE and DN, respectively, p < 0.05). Primary success, infarct rate and mortality were similar in all groups, but emergency bypass surgery was significantly higher in the DN (2.1% vs 0.8% in 1stRE and 0% in 2ndRE, p < 0.05). Restenosis can be effectively treated by redilatation. Patients with clinical and angiographic features predisposing to further recurrence can be better treated with other interventions (i.e., coronary stents, bypass surgery).

  20. Diffusion coefficient in photon diffusion theory

    NARCIS (Netherlands)

    Graaff, R; Ten Bosch, JJ

    2000-01-01

    The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to

  1. Tratamento endovascular da reestenose carotídea: resultados em curto prazo Endovascular treatment of carotid artery restenosis: short term results

    Directory of Open Access Journals (Sweden)

    Ricardo Augusto Carvalho Lujan

    2011-03-01

    Full Text Available CONTEXTO: O tratamento cirúrgico da reestenose carotídea apresenta alta taxa de lesão neurológica. Contrariamente, o tratamento endovascular da doença obstrutiva carotídea extracraniana tem se tornado mais factível e gradualmente menores taxas de risco cirúrgico vêm sendo reportadas, tornando-se uma opção em situações especiais, e provavelmente poderá ser considerado o tratamento padrão para reestenose carotídea. OBJETIVOS: Avaliar a aplicabilidade, a segurança e a eficácia da angioplastia com o uso do stent (ACS no tratamento da reestenose carotídea (REC no intraoperatório e no pós-operatório recente (80%, enquanto quatro (21% eram sintomáticos com estenose >70%. Apenas em um paciente não foi utilizado sistema de proteção cerebral. O sucesso técnico foi obtido em todos os casos. Não houve morte ou acidente vascular encefálico no intra ou no pós-operatório recente (30 dias. CONCLUSÃO: O tratamento endovascular da reestenose carotídea mostrou-se uma abordagem factível e segura em curto prazoCONTEXT: The surgical treatment of carotid artery restenosis presents a high risk of nerve injury. On the contrary, endovascular treatment for extracranial carotid artery obstructive disease has become more feasible. Gradually, lower rates of surgical risk have been reported, which makes the treatment a good option in special situations. It may be considered as the standard treatment for carotid artery restenosis. OBJECTIVE: To evaluate the applicability, safety, and efficacy of the angioplasty with the use of a stent (Carotid Artery Stenting - CAS for the treatment of carotid artery restenosis, in the intraoperative and early (80%, whereas 4 (21% were symptomatic with stenosis >70%. In only one patient a cerebral protection system was not used. Technical success was achieved in all cases. There was no death or stroke in the intraoperative or the early postoperative period (30 days. CONCLUSION: Endovascular treatment of

  2. HVJ-AVE liposome-mediated Tissue Factor Pathway Inhibitor (TFPI) gene transfer with recombinant TFPI (rTFPI) irrigation attenuates restenosis in atherosclerotic arteries.

    Science.gov (United States)

    Yin, Xinhua; Fu, Yu; Yutani, Chikao; Ikeda, Yoshihiko; Enjyoji, Keiichi; Kato, Hisao

    2009-06-26

    In this study, we investigate whether the combination of HVJ-AVE liposome-mediated TFPI gene transfer and recombinant TFPI (rTFPI) irrigation would reduce restenosis safely and more effectively. The results indicated that at 4 weeks after angioplasty, the MLD, EELA, IELA and LA of TFPI group and rTFPI group were markedly greater than those of the control groups, and those in the combination group were even greater. The mean IA, I/M, and the percentage of stenosis in TFPI gene group and rTFPI group were significantly reduced compared with control groups, and those in the combination group were even further reduced. Thrombosis in the TFPI gene group, rTFPI group and combination group was significantly reduced compared with the other control groups. The systemic coagulation status of treated animals was not significantly changed and no toxicity was observed in each group. So combination of TFPI gene transfer using HVJ-AVE liposomes and rTFPI irrigation could inhibit thrombosis and neointimal hyperplasia, and attenuate vascular remodeling and luminal stenosis more effectively than using each method alone. The combination method may be a more effective and safe strategy for the prevention of restenosis after angioplasty in humans.

  3. Diffusion archeology for diffusion progression history reconstruction.

    Science.gov (United States)

    Sefer, Emre; Kingsford, Carl

    2016-11-01

    Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.

  4. Matrix metalloproteinases 2 and 3 gene polymorphisms and the risk of target vessel revascularization after percutaneous coronary intervention: Is there still room for determining genetic variation of MMPs for assessment of an increased risk of restenosis?

    NARCIS (Netherlands)

    Verschuren, J. J. W.; Sampietro, M. L.; Pons, D.; Trompet, S.; Ewing, M. M.; Quax, P. H. A.; de Knijff, P.; Zwinderman, A. H.; de Winter, R. J.; Tio, R. A.; de Maat, M. P.; Doevendans, P. A. F. M.; Jukema, J. W.

    2010-01-01

    Objective: Mixed results have been reported of matrix metalloproteinases (MMP) and their association with restenosis after percutaneous coronary intervention (PCI). The current study examines whether multiple single nucleotide polymorphisms (SNPs), covering the full genomic region of MMP2 and MMP3,

  5. Nuclear Receptor Nurr1 Is Expressed In and Is Associated With Human Restenosis and Inhibits Vascular Lesion Formation In Mice Involving Inhibition of Smooth Muscle Cell Proliferation and Inflammation

    NARCIS (Netherlands)

    Bonta, Peter I.; Pols, Thijs W. H.; van Tiel, Claudia M.; Vos, Mariska; Arkenbout, E. Karin; Rohlena, Jakub; Koch, Karel T.; de Maat, Moniek P. M.; Tanck, Michael W. T.; de Winter, Robbert J.; Pannekoek, Hans; Biessen, Erik A. L.; Bot, Ilze; de Vries, Carlie J. M.

    2010-01-01

    Background-Restenosis is the major drawback of percutaneous coronary interventions involving excessive activation and proliferation of vascular smooth muscle cells (SMCs). The nuclear receptor Nurr1 is an early response gene known mainly for its critical role in the development of dopamine neurons.

  6. Long-term risk of carotid restenosis in patients randomly assigned to endovascular treatment or endarterectomy in the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS): long-term follow-up of a randomised trial.

    LENUS (Irish Health Repository)

    Bonati, Leo H

    2009-10-01

    In the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS), early recurrent carotid stenosis was more common in patients assigned to endovascular treatment than it was in patients assigned to endarterectomy (CEA), raising concerns about the long-term effectiveness of endovascular treatment. We aimed to investigate the long-term risks of restenosis in patients included in CAVATAS.

  7. Excess Entropy and Diffusivity

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Excess Entropy and Diffusivity. Excess entropy scaling of diffusivity (Rosenfeld,1977). Analogous relationships also exist for viscosity and thermal conductivity.

  8. Bile viscosity in patients with biliary drainage. Effect of co-trimoxazole and N-acetylcysteine and role in stent clogging

    NARCIS (Netherlands)

    Coene, P. P.; Groen, A. K.; Davids, P. H.; Hardeman, M.; Tytgat, G. N.; Huibregtse, K.

    1994-01-01

    The main disadvantage of endoscopic insertion of an endoprosthesis is the tendency of the stent to clog after a few months. In this study we determined the role of bile viscosity in stent clogging. Sixty patients were stented with 10 Fr 11-cm stents. The stents were electively removed after 2

  9. Intravascular ultrasound assessment of expansion of the sirolimus-eluting (Cypher Select) and paclitaxel-eluting (Taxus Express-2) stent in patients with diabetes mellitus

    DEFF Research Database (Denmark)

    Jensen, L.O.; Maeng, M.; Mintz, G.S.

    2008-01-01

    Patients with diabetes have a higher risk for in-stent restenosis after coronary stent implantation. Drug-eluting stents (DES) are highly effective in reducing in-stent restenosis. Once neointimal hyperplasia is suppressed with DES, the impact of stent underexpansion becomes magnified. The aim of...

  10. Association of morphologic characteristics on optical coherence tomography and angiographic progression patterns of late restenosis after drug-eluting stent implantation

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Hiroshi, E-mail: yhclinic@po5.synapse.ne.jp [Division of Cardiology, Tenyoukai Central Hospital, Izumi-cho, Kagoshima city, Kagoshima (Japan); Arikawa, Ryo; Takaoka, Junichiro; Miyamura, Akihiro; Atsuchi, Nobuhiko; Ninomiya, Toshiko; Atsuchi, Yoshihiko [Division of Cardiology, Tenyoukai Central Hospital, Izumi-cho, Kagoshima city, Kagoshima (Japan); Ohishi, Mitsuru [Department of Cardiovascular Medicine and Hypertension, Graduate School of Medical and Dental Science, Kagoshima University, Kagoshima (Japan); Terashima, Mitsuyasu [Department of Cardiology, Toyohashi Heart Center, Toyohashi (Japan); Kaneda, Hideaki [Okinaka Memorial Institute for Medical Research, Tokyo (Japan); Translational Research Informatics Center, Foundation for Biomedical Research and Innovation, Kobe (Japan)

    2015-01-15

    Objectives: To gain insight into the pathophysiology of late drug-eluting stent (DES) restenosis. Background: Restenosis of DES has a different time course from that of bare metal stents. Methods: Patients who underwent follow-up coronary angiography (CAG) twice (six to nine months and 18 to 24 months) after DES implantation were examined using optical coherence tomography (OCT). All lesions with target lesion revascularization at first follow-up were excluded. Late catch-up was defined as lesions that progressed from less than 50% diameter stenosis (DS) at the first CAG to more than 50% DS at the second CAG. Lesions with the late catch-up were further divided into two groups; lesions with jump-up (less than 25% DS at the first CAG) and lesions with gradual progression (25–50% DS at the first CAG). Results: Of the 25 patients who had late ISR, 23 patients (10 jump-up/13 gradual progression) were examined with OCT at late follow-up and enrolled in this study. In the qualitative OCT assessment, each ratio of homogeneous, layered, heterogeneous with or without attenuation tissue morphologies were in jump-up group, and gradual progression group were 0% and 15%, 0% and 23%, and 60% and 8%, and 40% and 54%, respectively. All of jump-up group showed heterogeneous restenotic tissue, while 62% of gradual progression group showed heterogeneous restenotic tissue (P = .04). Conclusions: These findings suggest different pathophysiology of the late catch-up after DES implantation between the jump-up and gradual progression groups.

  11. Diffusion in solids

    International Nuclear Information System (INIS)

    Tiwari, G.P.; Kale, G.B.; Patil, R.V.

    1999-01-01

    The article presents a brief survey of process of diffusion in solids. It is emphasised that the essence of diffusion is the mass transfer through the atomic jumps. To begin with formal equations for diffusion coefficient are presented. This is followed by discussions on mechanisms of diffusion. Except for solutes which form interstitial solid solution, diffusion in majority of cases is mediated through exchange of sites between an atom and its neighbouring vacancy. Various vacancy parameters such as activation volume, correlation factor, mass effect etc are discussed and their role in establishing the mode of diffusion is delineated. The contribution of dislocations and grain boundaries in diffusion process is brought out. The experimental determination of different types of diffusion coefficients are described. Finally, the pervasive nature of diffusion process in number of commercial processes is outlined to show the importance of diffusion studies in materials science and technology. (author)

  12. Diffusion archeology for diffusion progression history reconstruction

    OpenAIRE

    Sefer, Emre; Kingsford, Carl

    2015-01-01

    Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring — perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial d...

  13. Spin-diffusions and diffusive molecular dynamics

    Science.gov (United States)

    Farmer, Brittan; Luskin, Mitchell; Plecháč, Petr; Simpson, Gideon

    2017-12-01

    Metastable configurations in condensed matter typically fluctuate about local energy minima at the femtosecond time scale before transitioning between local minima after nanoseconds or microseconds. This vast scale separation limits the applicability of classical molecular dynamics (MD) methods and has spurned the development of a host of approximate algorithms. One recently proposed method is diffusive MD which aims at integrating a system of ordinary differential equations describing the likelihood of occupancy by one of two species, in the case of a binary alloy, while quasistatically evolving the locations of the atoms. While diffusive MD has shown itself to be efficient and provide agreement with observations, it is fundamentally a model, with unclear connections to classical MD. In this work, we formulate a spin-diffusion stochastic process and show how it can be connected to diffusive MD. The spin-diffusion model couples a classical overdamped Langevin equation to a kinetic Monte Carlo model for exchange amongst the species of a binary alloy. Under suitable assumptions and approximations, spin-diffusion can be shown to lead to diffusive MD type models. The key assumptions and approximations include a well-defined time scale separation, a choice of spin-exchange rates, a low temperature approximation, and a mean field type approximation. We derive several models from different assumptions and show their relationship to diffusive MD. Differences and similarities amongst the models are explored in a simple test problem.

  14. Microfabricated diffusion source

    Science.gov (United States)

    Oborny, Michael C [Albuquerque, NM; Frye-Mason, Gregory C [Cedar Crest, NM; Manginell, Ronald P [Albuquerque, NM

    2008-07-15

    A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.

  15. Investigation on the potential of thulium-fibre-laser irradiation for in-stent tissue ablation (Conference Presentation)

    Science.gov (United States)

    Sroka, Ronald; Frank, Johannes; Reichenberger, Frank; Behr, J.; Gesierich, Wolfgang

    2017-04-01

    Granulation and tumor regrowth in the area of bronchi stent implants may result in restenosis. It had been shown that by means of Thulium-Fibre-Laser (TFL) a controlled ablation and reduction of the tissue within the stent could be performed. When using Nd:YAG irradiation there is risk for explosive flames, burns of fibre and stent, ruptures of stent meshes as well as perforation of stent and cover. Therefore it was the aim to investigate the safety margin when using TFL. Four different types of clinical used stents (with/without cover) were fixed to pig trachea tissue. Irradiation was performed by fibre assisted TFL-1940nm-laser irradiation while laser power, light application duration and distance, as well as oxygen percentage and contamination were varied. In case of Nitinol-stents rupture were observed at power levels >=7W or distances of =5 mm and the power level should be <=6W. Furthermore the oxygen conc. should not exceed 30% and short term continuous irradiation of less than 15s exposition should be considered. In case of Silicon-stents light application on contaminated area should be avoided.

  16. Lung diffusion testing

    Science.gov (United States)

    ... medlineplus.gov/ency/article/003854.htm Lung diffusion testing To use the sharing features on this page, please enable JavaScript. Lung diffusion testing measures how well the lungs exchange gases. This ...

  17. Nonlinear ambipolar diffusion waves

    Energy Technology Data Exchange (ETDEWEB)

    Mendonca, J.T.; Rowlands, G.

    1985-07-01

    The evolution of a plasma perturbation in a neutral gas is considered using the ambipolar diffusion approximation. A nonlinear diffusion equation is derived and, in the one-dimensional case, exact solutions of shock type are obtained.

  18. Clinical outcomes of secondary stent-in-stent self-expanding metal stent placement for primary stent malfunction in malignant gastric outlet obstruction.

    Science.gov (United States)

    Park, Jun Chul; Park, Jae Jun; Cheoi, Kungseok; Chung, Hyunsoo; Lee, Hyuk; Shin, Sung Kwan; Lee, Sang Kil; Lee, Yong Chan

    2012-12-01

    Although a substantial number of patients require secondary stents insertion due to primary stent malfunction in malignant gastric outlet obstruction, data on the outcomes of secondary self-expanding metal stents are sparse. To investigate clinical outcomes and factors related with secondary stent malfunction in patients with malignant gastric outlet obstruction given secondary stent-in-stent self-expanding metal stent insertion. For this retrospective study, a total 77 patients who underwent secondary stent-in-stent self-expanding metal stent placement for primary stent malfunction in malignant gastric outlet obstruction were enrolled. We compared the effectiveness and complications of secondary covered and uncovered stents and explored the predictive factors for stent malfunction. Stent-in-stent self-expanding metal stent placements were technically successful in all patients. Both groups also had comparable clinical success rates (covered stent, 87.2% and uncovered stent, 90.0%, P = 1.000). Stent malfunction rates (31.9% and 36.7% respectively, P = 0.805) and median patency time of stent (165 [95% confidence interval: 112-218] and 165 [95% confidence interval: 126-204] days, respectively, P = 0.358) were similar between secondary covered and uncovered stents. Longer patients' survival time (≥ 100 days) was associated with increased risk of stent malfunction (odds ratio: 4.598; 95% confidence interval: 1.473-14.355; P = 0.009). Secondary stent-in-stent self-expanding metal stent placement is feasible and effective treatment for primary stent malfunctions in malignant gastric outlet obstruction. Covered and uncovered stent are equally acceptable in terms of stent-related complications and stent patency, regardless of primary stent type. Copyright © 2012 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

  19. Life-threatening bleeding from a vertebral artery pseudoaneurysm after anterior cervical spine approach: endovascular repair by a triple stent-in-stent method. Case report

    Energy Technology Data Exchange (ETDEWEB)

    Alzamora, M.G.; Klisch, J. [Section of Neuroradiology, Neurocenter, University of Freiburg (Germany); Rosahl, S.K.; Lehmberg, J. [Department of Neurosurgery, Neurocenter, University of Freiburg (Germany)

    2005-04-01

    The incidence of injury to the cervical vertebral artery during surgery for stenosis of the cervical neuroforamina is very low. We present a case in which bleeding during microforaminotomy at the level C6/7 occurred. The bleeding could be controlled intraoperatively. Two days later, a life-threatening cervical hematoma required urgent bedside evacuation. A false aneurysm of the left cervical vertebral artery was successfully occluded by a modified triple stent-in-stent technique, maintaining the flow in the vessel.

  20. Life-threatening bleeding from a vertebral artery pseudoaneurysm after anterior cervical spine approach: endovascular repair by a triple stent-in-stent method. Case report

    International Nuclear Information System (INIS)

    Alzamora, M.G.; Klisch, J.; Rosahl, S.K.; Lehmberg, J.

    2005-01-01

    The incidence of injury to the cervical vertebral artery during surgery for stenosis of the cervical neuroforamina is very low. We present a case in which bleeding during microforaminotomy at the level C6/7 occurred. The bleeding could be controlled intraoperatively. Two days later, a life-threatening cervical hematoma required urgent bedside evacuation. A false aneurysm of the left cervical vertebral artery was successfully occluded by a modified triple stent-in-stent technique, maintaining the flow in the vessel

  1. Fractional diffusion equations and anomalous diffusion

    CERN Document Server

    Evangelista, Luiz Roberto

    2018-01-01

    Anomalous diffusion has been detected in a wide variety of scenarios, from fractal media, systems with memory, transport processes in porous media, to fluctuations of financial markets, tumour growth, and complex fluids. Providing a contemporary treatment of this process, this book examines the recent literature on anomalous diffusion and covers a rich class of problems in which surface effects are important, offering detailed mathematical tools of usual and fractional calculus for a wide audience of scientists and graduate students in physics, mathematics, chemistry and engineering. Including the basic mathematical tools needed to understand the rules for operating with the fractional derivatives and fractional differential equations, this self-contained text presents the possibility of using fractional diffusion equations with anomalous diffusion phenomena to propose powerful mathematical models for a large variety of fundamental and practical problems in a fast-growing field of research.

  2. p21-Activated Kinase 4 Promotes Intimal Hyperplasia and Vascular Smooth Muscle Cells Proliferation during Superficial Femoral Artery Restenosis after Angioplasty

    Directory of Open Access Journals (Sweden)

    Liangxi Yuan

    2017-01-01

    Full Text Available The aim of this study is to explore the function of p21-activated kinase 4 (PAK4 in intimal hyperplasia (IH and vascular smooth muscle cells (VSMCs proliferation. We choose vascular samples from patients undergoing angioplasty in superficial femoral artery (SFA as the experimental group and vascular samples from donors without clinical SFA restenosis as the control group, respectively. We draw from the results that both levels of mRNA and protein of PAK4 in the experimental group increased dramatically compared with the control group. IH arose from angioplasty of SFA. Moreover, overexpression of PAK4 dramatically contributed to cell proliferation of VSMCs and promoted cell cycle progression from G0/G1 phase (71.12±0.69% versus 58.77±0.77%, P<0.001 into S phase (23.99±0.21% versus 31.35±0.33%, P<0.001. Besides, PAK4 downregulated the level of p21 and enhanced the activity of Akt as well. And we conclude that PAK4 acts as a regulator of cell cycle progression of VSMC by mediating Akt signaling and controlling p21 levels, which further modulate IH and VSMCs’ proliferation.

  3. Hereditary Diffuse Infiltrating Retinoblastoma.

    Science.gov (United States)

    Schedler, Katharina J E; Traine, Peter G; Lohmann, Dietmar R; Haritoglou, Christos; Metz, Klaus A; Rodrigues, Eduardo B

    2016-01-01

    Retinoblastoma is one of the most common childhood cancers. The diffuse infiltrating retinoblastoma is a rare subtype of this neoplasm. The majority of cases of diffuse infiltrating retinoblastoma are unilateral and occur sporadically. Herein we report on a family with three children affected by retinoblastoma, among them one girl with diffuse infiltrating retinoblastoma. This girl was diagnosed at the age of 8 years with a unilateral diffuse infiltrating retinoblastoma. By contrast, the two brothers became clinically apparent in the first 2 years of life with bilateral retinoblastoma. The parents were clinically unremarkable. Genetic analysis of RB1 gene was performed. The girl with diffuse infiltrating RB was found to be heterozygous for an oncogenic mutation in the RB1 gene that was also carried by both brothers and the father of the family. These results show that diffuse infiltrating retinoblastoma can develop on the background of a hereditary predisposition to retinoblastoma.

  4. Metric diffusion along foliations

    CERN Document Server

    Walczak, Szymon M

    2017-01-01

    Up-to-date research in metric diffusion along compact foliations is presented in this book. Beginning with fundamentals from the optimal transportation theory and the theory of foliations; this book moves on to cover Wasserstein distance, Kantorovich Duality Theorem, and the metrization of the weak topology by the Wasserstein distance. Metric diffusion is defined, the topology of the metric space is studied and the limits of diffused metrics along compact foliations are discussed. Essentials on foliations, holonomy, heat diffusion, and compact foliations are detailed and vital technical lemmas are proved to aide understanding. Graduate students and researchers in geometry, topology and dynamics of foliations and laminations will find this supplement useful as it presents facts about the metric diffusion along non-compact foliation and provides a full description of the limit for metrics diffused along foliation with at least one compact leaf on the two dimensions.

  5. Gaseous diffusion system

    International Nuclear Information System (INIS)

    Garrett, G.A.; Shacter, J.

    1978-01-01

    A gaseous diffusion system is described comprising a plurality of diffusers connected in cascade to form a series of stages, each of the diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof

  6. Inpainting using airy diffusion

    Science.gov (United States)

    Lorduy Hernandez, Sara

    2015-09-01

    One inpainting procedure based on Airy diffusion is proposed, implemented via Maple and applied to some digital images. Airy diffusion is a partial differential equation with spatial derivatives of third order in contrast with the usual diffusion with spatial derivatives of second order. Airy diffusion generates the Airy semigroup in terms of the Airy functions which can be rewritten in terms of Bessel functions. The Airy diffusion can be used to smooth an image with the corresponding noise elimination via convolution. Also the Airy diffusion can be used to erase objects from an image. We build an algorithm using the Maple package ImageTools and such algorithm is tested using some images. Our results using Airy diffusion are compared with the similar results using standard diffusion. We observe that Airy diffusion generates powerful filters for image processing which could be incorporated in the usual packages for image processing such as ImageJ and Photoshop. Also is interesting to consider the possibility to incorporate the Airy filters as applications for smartphones and smart-glasses.

  7. Oxygen Diffusion in Titanite

    Science.gov (United States)

    Zhang, X. Y.; Cherniak, D. J.; Watson, E. B.

    2004-05-01

    Oxygen diffusion in natural and synthetic single-crystal titanite was characterized under both dry and water-present conditions. For the dry experiments, pre-polished titanite samples were packed in 18O-enriched quartz powder inside Ag-Pd capsules, along with an FMQ buffer assemblage maintained physically separate by Ag-Pd strips. The sealed Ag-Pd capsules were themselves sealed inside evacuated silica glass tubes and run at 700-1050° C and atmospheric pressure for durations ranging from 1 hour to several weeks. The hydrothermal experiments were conducted by encapsulating polished titanite crystals with 18O enriched water and running them at 700-900° C and 10-160MPa in standard cold-seal pressure vessels for durations of 1 day to several weeks. Diffusive uptake profiles of 18O were measured in all cases by nuclear reaction analysis (NRA) using the 18O (p,α ) 15N reaction. For the experiments on natural crystals, under both dry and hydrothermal conditions, two mechanisms could be recognized responsible for oxygen diffusion. The diffusion profiles showed two segments: a steep one close to the initial surface attributed to self-diffusion in the titanite lattice; and a "tail" reaching deeper into the sample attributable to diffusion in a "fast path" such as sub-grain boundaries or dislocations. For the dry experiments, the following Arrhenius relation was obtained: D{dry lattice} = 2.6×10-8exp (-275 kJmol-1/RT) m2/s Under wet conditions at PH2O = 100MPa, Oxygen diffusion conforms to the following Arrehenius relation: D{wet lattice} = 9.7× 10-13exp (-174 kJmol-1/RT) m2/s Oxygen diffusivity shows only a slight dependence on water pressure at the following conditions we explored: temperatures 800° C, PH2O = 10-160MPa, and 880° C, PH2O =10-100MPa. For diffusive anisotropy, we explored it only at hydrothermal conditions, and no diffusive anisotropy was observed. Like many other silicates, titanite shows lower activation energy for oxygen diffusion in the presence of

  8. Modelling of Innovation Diffusion

    Directory of Open Access Journals (Sweden)

    Arkadiusz Kijek

    2010-01-01

    Full Text Available Since the publication of the Bass model in 1969, research on the modelling of the diffusion of innovation resulted in a vast body of scientific literature consisting of articles, books, and studies of real-world applications of this model. The main objective of the diffusion model is to describe a pattern of spread of innovation among potential adopters in terms of a mathematical function of time. This paper assesses the state-of-the-art in mathematical models of innovation diffusion and procedures for estimating their parameters. Moreover, theoretical issues related to the models presented are supplemented with empirical research. The purpose of the research is to explore the extent to which the diffusion of broadband Internet users in 29 OECD countries can be adequately described by three diffusion models, i.e. the Bass model, logistic model and dynamic model. The results of this research are ambiguous and do not indicate which model best describes the diffusion pattern of broadband Internet users but in terms of the results presented, in most cases the dynamic model is inappropriate for describing the diffusion pattern. Issues related to the further development of innovation diffusion models are discussed and some recommendations are given. (original abstract

  9. Thermal diffusion (1963)

    International Nuclear Information System (INIS)

    Lemarechal, A.

    1963-01-01

    This report brings together the essential principles of thermal diffusion in the liquid and gaseous phases. The macroscopic and molecular aspects of the thermal diffusion constant are reviewed, as well as the various measurement method; the most important developments however concern the operation of the CLUSIUS and DICKEL thermo-gravitational column and its applications. (author) [fr

  10. Diffusion Based Photon Mapping

    DEFF Research Database (Denmark)

    Schjøth, Lars; Olsen, Ole Fogh; Sporring, Jon

    2006-01-01

    . To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....

  11. Diffuse ceiling ventilation

    DEFF Research Database (Denmark)

    Zhang, Chen

    Diffuse ceiling ventilation is an innovative ventilation concept where the suspended ceiling serves as air diffuser to supply fresh air into the room. Compared with conventional ventilation systems, diffuse ceiling ventilation can significantly reduce or even eliminate draught risk due to the low...... momentum supply. In addition, this ventilation system uses a ceiling plenum to deliver air and requires less energy consumption for air transport than full-ducted systems. There is a growing interest in applying diffuse ceiling ventilation in offices and other commercial buildings due to the benefits from...... both thermal comfort and energy efficient aspects. The present study aims to characterize the air distribution and thermal comfort in the rooms with diffuse ceiling ventilation. Both the stand-alone ventilation system and its integration with a radiant ceiling system are investigated. This study also...

  12. Atomic diffusion in stars

    CERN Document Server

    Michaud, Georges; Richer, Jacques

    2015-01-01

    This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

  13. Diffusing Best Practices

    DEFF Research Database (Denmark)

    Pries-Heje, Jan; Baskerville, Richard

    2014-01-01

    resulting from the design were two-day training workshops conceptually anchored to TBP. The design theory was evaluated through execution of eight diffusion workshops involving three different groups in the same company. The findings indicate that the match between the practice and the context materialized...... in the successful techniques in one context. While the value for other contexts is unproven, knowledge of best practices circulates under an assumption that the practices will usefully self-diffuse through innovation and adoption in other contexts. We study diffusion of best practices using a design science...... approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...

  14. Degenerate nonlinear diffusion equations

    CERN Document Server

    Favini, Angelo

    2012-01-01

    The aim of these notes is to include in a uniform presentation style several topics related to the theory of degenerate nonlinear diffusion equations, treated in the mathematical framework of evolution equations with multivalued m-accretive operators in Hilbert spaces. The problems concern nonlinear parabolic equations involving two cases of degeneracy. More precisely, one case is due to the vanishing of the time derivative coefficient and the other is provided by the vanishing of the diffusion coefficient on subsets of positive measure of the domain. From the mathematical point of view the results presented in these notes can be considered as general results in the theory of degenerate nonlinear diffusion equations. However, this work does not seek to present an exhaustive study of degenerate diffusion equations, but rather to emphasize some rigorous and efficient techniques for approaching various problems involving degenerate nonlinear diffusion equations, such as well-posedness, periodic solutions, asympt...

  15. Oxygen diffusion in monazite

    Science.gov (United States)

    Cherniak, D. J.; Zhang, X. Y.; Nakamura, M.; Watson, E. B.

    2004-09-01

    We report measurements of oxygen diffusion in natural monazites under both dry, 1-atm conditions and hydrothermal conditions. For dry experiments, 18O-enriched CePO4 powder and monazite crystals were sealed in Ag-Pd capsules with a solid buffer (to buffer at NNO) and annealed in 1-atm furnaces. Hydrothermal runs were conducted in cold-seal pressure vessels, where monazite grains were encapsulated with 18O-enriched water. Following the diffusion anneals, oxygen concentration profiles were measured with Nuclear Reaction Analysis (NRA) using the reaction 18O(p,α)15N. Over the temperature range 850-1100 °C, the Arrhenius relation determined for dry diffusion experiments on monazite is given by: Under wet conditions at 100 MPa water pressure, over the temperature range 700-880 °C, oxygen diffusion can be described by the Arrhenius relationship: Oxygen diffusion under hydrothermal conditions has a significantly lower activation energy for diffusion than under dry conditions, as has been found the case for many other minerals, both silicate and nonsilicate. Given these differences in activation energies, the differences between dry and wet diffusion rates increase with lower temperatures; for example, at 600 °C, dry diffusion will be more than 4 orders of magnitude slower than diffusion under hydrothermal conditions. These disparate diffusivities will result in pronounced differences in the degree of retentivity of oxygen isotope signatures. For instance, under dry conditions (presumably rare in the crust) and high lower-crustal temperatures (∼800 °C), monazite cores of 70-μm radii will preserve O isotope ratios for about 500,000 years; by comparison, they would be retained at this temperature under wet conditions for about 15,000 years.

  16. Solving the Issue of Restenosis After Stenting of Intracranial Stenoses: Experience with Two Thin-Strut Drug-Eluting Stents (DES)—Taxus Element™ and Resolute Integrity™

    Energy Technology Data Exchange (ETDEWEB)

    Kurre, Wiebke, E-mail: wiebke.kurre@gmx.de; Aguilar-Pérez, Marta [Klinikum Stuttgart, Klinik für Diagnostische und Interventionelle Neuroradiologie (Germany); Fischer, Sebastian [Universitätsklinikum Knappschaftskrankenhaus Bochum GmbH, Institut für Diagnostische und Interventionelle Radiologie, Neuroradiologie und Nuklearmedizin (Germany); Arnold, Guy [Klinikverbund Südwest, Klinikum Sindelfingen, Klinik für Neurologie (Germany); Schmid, Elisabeth; Bäzner, Hansjörg [Klinikum Stuttgart, Klinik für Neurologie (Germany); Henkes, Hans [Klinikum Stuttgart, Klinik für Diagnostische und Interventionelle Neuroradiologie (Germany)

    2015-06-15

    PurposeThin-strut, flexible DES are suitable for intracranial stenting and may improve long-term vessel patency. The purpose of this study was to report our experience with two new-generation DES for the treatment of intracranial atherosclerotic disease.Patients and MethodsWe retrospectively reviewed all patients treated with Taxus Element™ or Resolute Integrity™ stent for an intracranial atherosclerotic stenosis between March 2011 and August 2013. Technical success was defined as the ability to deploy the device at the desired location and reduce the degree of stenosis below 50 %. All procedure-related strokes were recorded. Control angiography was scheduled after 6 weeks, 3, 6, and 12 months and yearly thereafter. A luminal narrowing ≥50 % was regarded as a restenosis. Stroke recurrence in the territory of the treated artery was reported.ResultsIn the defined period we treated 101 patients harboring 117 intracranial stenoses. The procedure was successful in 100 (85.5 %) lesions. Procedure-related strokes occurred in 10 (9.9 %) patients with a permanent morbidity in 3 (3.0 %). Follow-up angiography was available for 83 of 100 (83.0 %) successfully treated lesions with an average of 355 days (IQR 153–482 days). Three (3.6 %) asymptomatic restenoses were detected. All occurred after treatment with Resolute Integrity™, none after Taxus Element™ (p = 0.059). New strokes in the territory of the treated artery were encountered in 2 (2.6 %) occasions.ConclusionThin-strut DES improve long-term patency and reduce the risk of subsequent stroke. Differences between devices may exist. Feasibility is comparable to bare-metal balloon-mounted stents and procedure-related strokes occurred within the expected range.

  17. Comparison of Recanalization and In-Stent Stenosis Between the Low-Profile Visualized Intraluminal Support Stent and Enterprise Stent-Assisted Coiling for 254 Intracranial Aneurysms.

    Science.gov (United States)

    Feng, Xin; Qian, Zenghui; Liu, Peng; Zhang, Baorui; Wang, Luyao; Guo, Erkang; Wen, Xiaolong; Xu, Wenjuan; Jiang, Chuhan; Wu, Zhongxue; Li, Youxiang; Liu, Aihua

    2018-01-01

    To compare the rates of recanalization and in-stent stenosis between the Enterprise (EP) and low-profile visualized intraluminal support (LVIS) stent deployments for intracranial aneurysms (IAs), and the factors associated therein. Between June 2014 and July 2016, 142 patients with a total of 161 IAs were treated by LVIS stent-assisted coiling and 111 patients with a total of 142 IAs were treated by EP stent-assisted coiling at our institution. Procedure-related complications, angiographic follow-up results, and clinical outcomes were analyzed statistically. The rates of initially complete and near-complete IA occlusion immediately after the procedure were similar in the LVIS and EP groups (94.3% vs. 89.9%; P = 0.275). On follow-up, complete and near-complete occlusion rates and recanalization rates were also similar in the 2 groups (96.6% vs. 92.1%; P =0.330 and 8.0% vs. 13.5%; P = 0.245, respectively). On logistic regression analysis, a higher size ratio (SR) was significantly associated with the recanalization of aneurysms in the EP group, but not in the LVIS group. The rate of moderate to severe in-stent stenosis was lower in the LVIS group (10.2%) than in the EP group (16.8%), but the difference was not statistically significant (P = 0.198). Our data show acceptable rates of complete and near-complete occlusion with both the LVIS and EP stents. LVIS stents were associated with lower rates of recanalization and in-stent stenosis, but the difference was not significant. Higher SR (≥2) was a significant predictor of recanalization in IAs treated with EP stents, but not in those treated with LVIS stents. Copyright © 2017. Published by Elsevier Inc.

  18. Bioresorbable vascular scaffold (BVS) for in-stent chronic total occlusion: Antegrade recanalization and IVUS-guided BVS implantation by radial access

    Energy Technology Data Exchange (ETDEWEB)

    Medda, Massimo [Interventional Cardiology Unit, Istituto Clinico Sant' Ambrogio, Milano (Italy); Casilli, Francesco, E-mail: frcasill@tin.it [Interventional Cardiology Unit, Istituto Clinico Sant' Ambrogio, Milano (Italy); Bande, Marta [Interventional Cardiology Unit, Istituto Clinico Sant' Ambrogio, Milano (Italy); Latini, Maria Giulia [Cardiologia Interventistica, IRCCS Policlinico San Donato, San Donato Milanese, Milano (Italy); Ghommidh, Mehdi [Interventional Cardiology Unit, Istituto Clinico Sant' Ambrogio, Milano (Italy); Del Furia, Francesca [Unità Operativa di Cardiologia, Azienda Ospedaliera di Melegnano, Milano (Italy); Inglese, Luigi [Interventistica Cardiovascolare, Gruppo Sanitario Policlinico di Monza, Milano (Italy)

    2016-01-15

    The completely absorbable stents represent one of the latest innovations in the field of interventional cardiology, prospecting the possibility of “vascular repair”. In the published trials (ABSORB Cohort A and B, ABSORB EXTEND, and ABSORB II, III and IV) chronic total occlusions (CTOs) were considered an exclusion criteria. More recently the CTO-ABSORB pilot study demonstrated the safety and feasibility of bioresorbable vascular scaffold (BVS) use in case of CTO recanalization. We present the first case, to our knowledge, of in-stent occlusion successfully treated with an everolimus-eluting BVS and discuss its potential advantages in such kind of lesions.

  19. Diffuse interstellar clouds

    International Nuclear Information System (INIS)

    Black, J.H.

    1987-01-01

    The author defines and discusses the nature of diffuse interstellar clouds. He discusses how they contribute to the general extinction of starlight. The atomic and molecular species that have been identified in the ultraviolet, visible, and near infrared regions of the spectrum of a diffuse cloud are presented. The author illustrates some of the practical considerations that affect absorption line observations of interstellar atoms and molecules. Various aspects of the theoretical description of diffuse clouds required for a full interpretation of the observations are discussed

  20. Self diffusion in tungsten

    International Nuclear Information System (INIS)

    Mundy, J.N.; Rothman, S.J.; Lam, N.Q.; Nowicki, L.J.; Hoff, H.A.

    1978-01-01

    The lack of understanding of self-diffusion in Group VI metals together with the wide scatter in the measured values of tungsten self-diffusion has prompted the present measurements to be made over a wide temperature range (1/2Tsub(m) to Tsub(m)). The diffusion coefficients have been measured in the temperature range 1430-2630 0 C. The present measurements show non-linear Arrhenius behavior but a reliable two-exponential fit of the data should await further measurements. (Auth.)

  1. Diffuse Ceiling Ventilation

    DEFF Research Database (Denmark)

    Zhang, Chen; Yu, Tao; Heiselberg, Per Kvols

    -cooling period and night cooling potential. The investment cost of this ventilation system is about 5-10% lower than the conventional ones, because the acoustic ceiling could be directly applied as air diffuser and the use of plenum to distribute air reduces the cost of ductwork. There is a growing interest...... in applying diffuse ceiling ventilation in offices and other commercial buildings because of the benefits from both thermal comfort and energy efficiency aspects. The design guide introduces the principle and key characteristics of room air distribution with diffuse ceiling ventilation and the design...

  2. Diffuse Ceiling Ventilation

    DEFF Research Database (Denmark)

    Zhang, Chen; Yu, Tao; Heiselberg, Per Kvols

    -cooling period and night cooling potential. The investment cost of this ventilation system is about 5-10% lower than the conventional ones, because the acoustic ceiling could be directly applied as air diffuser and the use of plenum to distribute air reduces the cost of ductwork. There is a growing interest...... and manufacturers and the users of diffuse ceiling technology. The design guide introduces the principle and key characteristics of room air distribution with diffuse ceiling ventilation. It provides an overview of potential benefit and limitations of this technology. The benefits include high thermal comfort, high...

  3. Theories on diffusion of technology

    DEFF Research Database (Denmark)

    Munch, Birgitte

    Tracing the body of the diffusion proces by analysing the diffusion process from historical, sociological, economic and technical approaches. Discussing central characteristics of the proces of diffusion og CAD/CAM in Denmark....

  4. Diffusion of Wilson loops

    International Nuclear Information System (INIS)

    Brzoska, A.M.; Lenz, F.; Thies, M.; Negele, J.W.

    2005-01-01

    A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops is formulated as a symmetry property related to the center symmetry of the underlying gauge theory. The results are expressed in terms of an effective Wilson loop action and compared with various limits of SU(2) Yang-Mills theory

  5. On Diffusion and Permeation

    KAUST Repository

    Peppin, Stephen S. L.

    2009-01-01

    Diffusion and permeation are discussed within the context of irreversible thermodynamics. A new expression for the generalized Stokes-Einstein equation is obtained which links the permeability to the diffusivity of a two-component solution and contains the poroelastic Biot-Willis coefficient. The theory is illustrated by predicting the concentration and pressure profiles during the filtration of a protein solution. At low concentrations the proteins diffuse independently while at higher concentrations they form a nearly rigid porous glass through which the fluid permeates. The theoretically determined pressure drop is nonlinear in the diffusion regime and linear in the permeation regime, in quantitative agreement with experimental measurements. © 2009 Walter de Gruyter, Berlin, New York.

  6. Computational Diffusion MRI

    CERN Document Server

    Grussu, Francesco; Ning, Lipeng; Tax, Chantal; Veraart, Jelle

    2018-01-01

    This volume presents the latest developments in the highly active and rapidly growing field of diffusion MRI. The reader will find numerous contributions covering a broad range of topics, from the mathematical foundations of the diffusion process and signal generation, to new computational methods and estimation techniques for the in-vivo recovery of microstructural and connectivity features, as well as frontline applications in neuroscience research and clinical practice. These proceedings contain the papers presented at the 2017 MICCAI Workshop on Computational Diffusion MRI (CDMRI’17) held in Québec, Canada on September 10, 2017, sharing new perspectives on the most recent research challenges for those currently working in the field, but also offering a valuable starting point for anyone interested in learning computational techniques in diffusion MRI. This book includes rigorous mathematical derivations, a large number of rich, full-colour visualisations and clinically relevant results. As such, it wil...

  7. Isomorphism, Diffusion and Decoupling

    DEFF Research Database (Denmark)

    Boxenbaum, Eva; Jonsson, Stefan

    2017-01-01

    This chapter traces the evolution of the core theoretical constructs of isomorphism, decoupling and diffusion in organizational institutionalism. We first review the original theoretical formulations of these constructs and then examine their evolution in empirical research conducted over the past...

  8. Resilient Diffusive Clouds

    Science.gov (United States)

    2017-02-01

    RESILIENT DIFFUSIVE CLOUDS TRUSTEES OF DARTMOUTH COLLEGE FEBRUARY 2017 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC...To) SEP 2011 – SEP 2016 4. TITLE AND SUBTITLE RESILIENT DIFFUSIVE CLOUDS 5a. CONTRACT NUMBER FA8750-11-2-0257 5b. GRANT NUMBER N/A 5c. PROGRAM...diversified virtual machines. The concepts lead to a view of cloud computing in which vulnerabilities are different at every host, attackers cannot

  9. Advanced manufacturing: Technology diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Tesar, A.

    1995-12-01

    In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.

  10. Low-Profile Diffuser

    Science.gov (United States)

    Martin, Michael A.; Nettles, Mindy

    2015-01-01

    The propellant tanks used in liquid rockets require pressurization gases in order to maintain tank pressure while the tanks are being drained during engine operation. The pressurization gas, which is typically much warmer than the relatively cold propellants in the tank, must be introduced into the empty ullage space at the top of the tank. The purpose of the diffuser is to control the flow of the gas into the tank in order to prevent direct impingement of the gas on the liquid surface and/or the tank walls. If the diffuser did not perform those tasks, the warm gas can create excess heat transfer causing an increase in the amount of pressurization mass required. Typical diffusers are long vertical cylinders that create a large exit area in order to minimize gas velocities. However, long vertical cylinders limit the amount of liquid that can be loaded into the tank in order not to have the liquid surface near the diffuser. A design goal for a pressurization diffuser is to create uniform flow in order to prevent jets that can impact the liquid surface and/or tank walls. The purpose of the task was to create a diffuser design that had a lower vertical profile (in order to be able to raise the liquid surface) while still maintaining uniform flow.

  11. Successful stent-in-stent insertion of an expandable metallic stent covered with polyuretane placed to obliterate a large bronchial fistula after chemoradiotherapy for inoperable lung cancer

    International Nuclear Information System (INIS)

    Minami, Hiroya; Tsubota, Noriaki; Miyamoto, Yoshifumi; Yoshimura, Masahiro; Obayashi, Kayoko; Takada, Yoshiki

    1999-01-01

    Bronchial fistulas in cases of inoperable lung cancer caused by radiochemotherapy are quite refractory and generally cannot be surgically closed. A 45-year-old man with squamous cell carcinoma in the right lung underwent two courses of induction chemotherapy (135 mg CDDP, 5 mg VDS, 13.5 mg MMC) and radiation therapy (2 Gy x 22 times) for invasion of the right main bronchus, the pulmonary artery and superior vena cava. Just before the end of the second course, the empyem second to the bronchial fistula caused by tumor necrosis developed in the right upper bronchus, and fenestration was performed. After the operation, his condition improved remarkably, however the fistula enlarged into the right main bronchus and the purulent discharge flowed into the left lung. An expandable metallic stent (EMS) covered with polyuretane was inserted in the trachea and the left main bronchus to break aspiration pneumonia. As the covered EMS was too unstable to be fixed, a bare EMS was inserted in a stent-in-stent fashion. After the procedure he was followed at the O.P.D. and lived a relatively comfortable life for 9 months until his death due to tumor. We inserted the covered EMS in a stent-in-stent fashion to successfully obliterate a large bronchial fistula. (author)

  12. Transient Enhanced Diffusion

    Science.gov (United States)

    Gossmann, Hans-Joachim L.

    1996-03-01

    Ion implantation is the standard method for dopant introduction during integrated circuit manufacturing, determining crucial device characteristics. Implantation creates point-defects, such as Si self-interstitials and vacancies, far in excess of equilibrium concentrations. Since the diffusion of common dopants involves Si point defects, the interaction of damage and dopants during subsequent annealing steps leads to the phenomenon known as "transient enhanced diffusion" (TED): The dopant diffusivities are enhanced, possibly by many orders of magnitude. The enhancement is transient since the intrinsic defects eventually diffuse into the bulk or annihilate at the surface. The desired specific dopant profile of the device is thus the result of a complex reaction, involving the creation of damage and its spatial distribution, diffusion, and interaction of the point defects among themselves and with interfaces and other defects. As device dimensions shrink and experiments become more and more expensive, the capability to predict these kinds of non-equilibrium phenomena accurately becomes crucial to Si technology development. In our experiments to extract physical mechanisms and parameters of TED we use the method of sharp B- and Sb doping spikes to track interstitial and vacancy concentrations as a function of depth during processing. Thus we gain sensitivity to small diffusion distances (low temperatures) and separate the damaged region from the region of the interaction with dopants. In addition, our method yields directly the actual point defect diffusivity. Although an ion implant initially produces Frenkel pairs, Monte-carlo simulations show that the vacancies annihilate quickly. The excess interstitials, roughly one for each implanted ion coalesce into 311defects. The subsequent evaporation of interstitials from 311ś drives TED. Si interstitial diffusion is influenced by carbon-related traps and we will demonstrate that this finding reconciles quantitatively a

  13. Erythropoietin prevention trial of coronary restenosis and cardiac remodeling after ST-elevated acute myocardial infarction (EPOC-AMI): a pilot, randomized, placebo-controlled study.

    Science.gov (United States)

    Taniguchi, Norimasa; Nakamura, Takeshi; Sawada, Takahisa; Matsubara, Kinya; Furukawa, Keizo; Hadase, Mitsuyoshi; Nakahara, Yoshifumi; Nakamura, Takashi; Matsubara, Hiroaki

    2010-11-01

    Erythropoietin (EPO) enhances re-endothelialization and anti-apoptotic action. Larger clinical studies to examine the effects of high-dose EPO are in progress in patients with acute myocardial infarction (AMI). The aim of this multi-center pilot study was to investigate the effect of `low-dose EPO' (6,000 IU during percutaneous coronary intervention (PCI), 24 h and 48 h) in 35 patients with a first ST-elevated AMI undergoing PCI who was randomly assigned to EPO or placebo (saline) treatment. Neointimal volume, cardiac function and infarct size were examined in the acute phase and 6 months later (ClinicalTrials.gov identifier: NCT00423020). No significant regression in in-stent neointimal volume was observed, whereas left ventricular (LV) ejection fraction was significantly improved (49.2% to 55.7%, P=0.003) and LV end-systolic volume was decreased in the EPO group (47.7 ml to 39.0 ml, P=0.036). LV end-diastolic volume tended to be reduced from 90.2% to 84.5% (P=0.159), whereas in the control group it was inversely increased (91.7% to 93.7%, P=0.385). Infarction sizes were significantly reduced by 38.5% (P=0.003) but not in the control group (23.7%, P=0.051). Hemoglobin, peak creatine kinase values, and CD34(+)/CD133(+)/CD45(dim) endothelial progenitors showed no significant changes. No adverse events were observed during study periods. This is a first study demonstrating that short-term `low-dose' EPO to PCI-treated AMI patients did not prevent neointimal hyperplasia but rather improved cardiac function and infarct size without any clinical adverse effects.

  14. Lead diffusion in monazite

    International Nuclear Information System (INIS)

    Gardes, E.

    2006-06-01

    Proper knowledge of the diffusion rates of lead in monazite is necessary to understand the U-Th-Pb age anomalies of this mineral, which is one of the most used in geochronology after zircon. Diffusion experiments were performed in NdPO 4 monocrystals and in Nd 0.66 Ca 0.17 Th 0.17 PO 4 polycrystals from Nd 0.66 Pb 0.17 Th 0.17 PO 4 thin films to investigate Pb 2+ + Th 4+ ↔ 2 Nd 3+ and Pb 2+ ↔ Ca 2+ exchanges. Diffusion annealings were run between 1200 and 1500 Celsius degrees, at room pressure, for durations ranging from one hour to one month. The diffusion profiles were analysed using TEM (transmission electronic microscopy) and RBS (Rutherford backscattering spectroscopy). The diffusivities extracted for Pb 2+ + Th 4+ ↔ 2 Nd 3+ exchange follow an Arrhenius law with parameters E equals 509 ± 24 kJ mol -1 and log(D 0 (m 2 s -1 )) equals -3.41 ± 0.77. Preliminary data for Pb 2+ ↔ Ca 2+ exchange are in agreement with this result. The extrapolation of our data to crustal temperatures yields very slow diffusivities. For instance, the time necessary for a 50 μm grain to lose all of its lead at 800 Celsius degrees is greater than the age of the Earth. From these results and other evidence from the literature, we conclude that most of the perturbations in U-Th-Pb ages of monazite cannot be attributed to lead diffusion, but rather to interactions with fluids. (author)

  15. Sirolimus inhibits key events of restenosis in vitro/ex vivo: evaluation of the clinical relevance of the data by SI/MPL- and SI/DES-ratio's

    Directory of Open Access Journals (Sweden)

    Kountides Margaratis

    2007-05-01

    Full Text Available Abstract Background Sirolimus (SRL, Rapamycin has been used successfully to inhibit restenosis both in drug eluting stents (DES and after systemic application. The current study reports on the effects of SRL in various human in vitro/ex vivo models and evaluates the theoretical clinical relevance of the data by SI/MPL- and SI/DES-ratio's. Methods Definition of the SI/MPL-ratio: relation between significant inhibitory effects in vitro/ex vivo and the maximal plasma level after systemic administration in vivo (6.4 ng/ml for SRL. Definition of the SI/DES-ratio: relation between significant inhibitory effects in vitro/ex vivo and the drug concentration in DES (7.5 mg/ml in the ISAR drug-eluting stent platform. Part I of the study investigated in cytoflow studies the effect of SRL (0.01–1000 ng/ml on TNF-α induced expression of intercellular adhesion molecule 1 (ICAM-1 in human coronary endothelial cells (HCAEC and human coronary smooth muscle cells (HCMSMC. Part II of the study analysed the effect of SRL (0.01–1000 ng/ml on cell migration of HCMSMC. In part III, IV, and V of the study ex vivo angioplasty (9 bar was carried out in a human organ culture model (HOC-model. SRL (50 ng/ml was added for a period of 21 days, after 21 and 56 days cell proliferation, apoptosis, and neointimal hyperplasia was studied. Results Expression of ICAM-1 was significantly inhibited both in HCAEC (SRL ≥ 0.01 ng/ml and HCMSMC (SRL ≥ 10 ng/ml. SRL in concentrations ≥ 0.1 ng/ml significantly inhibited migration of HCMSMC. Cell proliferation and neointimal hyperplasia was inhibited at day 21 and day 56, significance (p Conclusion SI/MPL-ratio's ≤ 1 (ICAM-1 expression, cell migration characterize inhibitory effects of SRL that can be theoretically expected both after systemic and local high dose administration, a SI/MPL-ratio of 7.81 (cell proliferation represents an effect that was achieved with drug concentrations 7.81-times the MPL. SI/DES-ratio's between 10

  16. Anomalous Diffusion Near Resonances

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Tanaji; /Fermilab

    2010-05-01

    Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations. Transport of particles near resonances is still not a well understood phenomenon. Often, without justification, phase space motion is assumed to be a normal diffusion process although at least one case of anomalous diffusion in beam dynamics has been reported [1]. Here we will focus on the motion near synchro-betatron resonances which can be excited by several means, including beams crossing at an angle at the collision points as in the LHC. We will consider low order resonances which couple the horizontal and longitudinal planes, both for simplicity and to observe large effects over short time scales. While the tunes we consider are not practical for a collider, nonetheless the transport mechanisms we uncover are also likely to operate at higher order resonances.

  17. Distributed Control Diffusion

    DEFF Research Database (Denmark)

    Schultz, Ulrik Pagh

    2007-01-01

    . Programming a modular, self-reconfigurable robot is however a complicated task: the robot is essentially a real-time, distributed embedded system, where control and communication paths often are tightly coupled to the current physical configuration of the robot. To facilitate the task of programming modular....... This approach allows the programmer to dynamically distribute behaviors throughout a robot and moreover provides a partial abstraction over the concrete physical shape of the robot. We have implemented a prototype of a distributed control diffusion system for the ATRON modular, self-reconfigurable robot......, self-reconfigurable robots, we present the concept of distributed control diffusion: distributed queries are used to identify modules that play a specific role in the robot, and behaviors that implement specific control strategies are diffused throughout the robot based on these role assignments...

  18. Cesium diffusion in graphite

    International Nuclear Information System (INIS)

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of 137 Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of 137 Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000 0 C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ΔE of the equation D/epsilon = (D/epsilon) 0 exp [-ΔE/RT] are about 4 x 10 -2 cm 2 /s and 30 kcal/mole, respectively

  19. Apparatus for diffusion separation

    International Nuclear Information System (INIS)

    Nierenberg, W.A.; Pontius, R.B.

    1976-01-01

    The method of testing the separation efficiency of porous permeable membranes is described which comprises causing a stream of a gaseous mixture to flow into contact with one face of a finely porous permeable membrane under such conditions that a major fraction of the mixture diffuses through the membrane, maintaining a rectangular cross section of the gaseous stream so flowing past said membrane, continuously recirculating the gas that diffuses through said membrane and continuously withdrawing the gas that does not diffuse through said membrane and maintaining the volume of said recirculating gas constant by continuously introducing into said continuously recirculating gas stream a mass of gas equivalent to that which is continuously withdrawn from said gas stream and comparing the concentrations of the light component in the entering gas, the withdrawn gas and the recirculated gas in order to determine the efficiency of said membrane

  20. Diffusion in flexible pipes

    Energy Technology Data Exchange (ETDEWEB)

    Brogaard Kristensen, S.

    2000-06-01

    This report describes the work done on modelling and simulation of the complex diffusion of gas through the wall of a flexible pipe. The diffusion and thus the pressure in annulus depends strongly on the diffusion and solubility parameters of the gas-polymer system and on the degree of blocking of the outer surface of the inner liner due to pressure reinforcements. The report evaluates the basis modelling required to describe the complex geometries and flow patterns. Qualitatively results of temperature and concentration profiles are shown in the report. For the program to serve any modelling purpose in 'real life' the results need to be validated and possibly the model needs corrections. Hopefully, a full-scale test of a flexible pipe will provide the required temperatures and pressures in annulus to validate the models. (EHS)

  1. Diffusion and mass transfer

    CERN Document Server

    Vrentas, James S

    2013-01-01

    The book first covers the five elements necessary to formulate and solve mass transfer problems, that is, conservation laws and field equations, boundary conditions, constitutive equations, parameters in constitutive equations, and mathematical methods that can be used to solve the partial differential equations commonly encountered in mass transfer problems. Jump balances, Green’s function solution methods, and the free-volume theory for the prediction of self-diffusion coefficients for polymer–solvent systems are among the topics covered. The authors then use those elements to analyze a wide variety of mass transfer problems, including bubble dissolution, polymer sorption and desorption, dispersion, impurity migration in plastic containers, and utilization of polymers in drug delivery. The text offers detailed solutions, along with some theoretical aspects, for numerous processes including viscoelastic diffusion, moving boundary problems, diffusion and reaction, membrane transport, wave behavior, sedime...

  2. The Trouble with Diffusion

    Directory of Open Access Journals (Sweden)

    R.T. DeHoff

    2002-09-01

    Full Text Available The phenomenological formalism, which yields Fick's Laws for diffusion in single phase multicomponent systems, is widely accepted as the basis for the mathematical description of diffusion. This paper focuses on problems associated with this formalism. This mode of description of the process is cumbersome, defining as it does matrices of interdiffusion coefficients (the central material properties that require a large experimental investment for their evaluation in three component systems, and, indeed cannot be evaluated for systems with more than three components. It is also argued that the physical meaning of the numerical values of these properties with respect to the atom motions in the system remains unknown. The attempt to understand the physical content of the diffusion coefficients in the phenomenological formalism has been the central fundamental problem in the theory of diffusion in crystalline alloys. The observation by Kirkendall that the crystal lattice moves during diffusion led Darken to develop the concept of intrinsic diffusion, i.e., atom motion relative to the crystal lattice. Darken and his successors sought to relate the diffusion coefficients computed for intrinsic fluxes to those obtained from the motion of radioactive tracers in chemically homogeneous samples which directly report the jump frequencies of the atoms as a function of composition and temperature. This theoretical connection between tracer, intrinsic and interdiffusion behavior would provide the basis for understanding the physical content of interdiffusion coefficients. Definitive tests of the resulting theoretical connection have been carried out for a number of binary systems for which all three kinds of observations are available. In a number of systems predictions of intrinsic coefficients from tracer data do not agree with measured values although predictions of interdiffusion coefficients appear to give reasonable agreement. Thus, the complete

  3. Hydrogen diffusion in Zircon

    Science.gov (United States)

    Ingrin, Jannick; Zhang, Peipei

    2016-04-01

    Hydrogen mobility in gem quality zircon single crystals from Madagascar was investigated through H-D exchange experiments. Thin slices were annealed in a horizontal furnace flushed with a gas mixture of Ar/D2(10%) under ambient pressure between 900 ° C to 1150 ° C. FTIR analyses were performed on oriented slices before and after each annealing run. H diffusion along [100] and [010] follow the same diffusion law D = D0exp[-E /RT], with log D0 = 2.24 ± 1.57 (in m2/s) and E = 374 ± 39 kJ/mol. H diffusion along [001] follows a slightly more rapid diffusion law, with log D0 = 1.11 ± 0.22 (in m2/s) and E = 334 ± 49 kJ/mol. H diffusion in zircon has much higher activation energy and slower diffusivity than other NAMs below 1150 ° C even iron-poor garnets which are known to be among the slowest (Blanchard and Ingrin, 2004; Kurka et al. 2005). During H-D exchange zircon incorporates also deuterium. This hydration reaction involves uranium reduction as it is shown from the exchange of U5+ and U4+ characteristic bands in the near infrared region during annealing. It is the first time that a hydration reaction U5+ + OH- = U4+ + O2- + 1/2H2, is experimentally reported. The kinetics of deuterium incorporation is slightly slower than hydrogen diffusion, suggesting that the reaction is limited by hydrogen mobility. Hydrogen isotopic memory of zircon is higher than other NAMs. Zircons will be moderately retentive of H signatures at mid-crustal metamorphic temperatures. At 500 ° C, a zircon with a radius of 300 μm would retain its H isotopic signature over more than a million years. However, a zircon is unable to retain this information for geologically significant times under high-grade metamorphism unless the grain size is large enough. Refrences Blanchard, M. and Ingrin, J. (2004) Hydrogen diffusion in Dora Maira pyrope. Physics and Chemistry of Minerals, 31, 593-605. Kurka, A., Blanchard, M. and Ingrin, J. (2005) Kinetics of hydrogen extraction and deuteration in

  4. Phase transformation and diffusion

    CERN Document Server

    Kale, G B; Dey, G K

    2008-01-01

    Given that the basic purpose of all research in materials science and technology is to tailor the properties of materials to suit specific applications, phase transformations are the natural key to the fine-tuning of the structural, mechanical and corrosion properties. A basic understanding of the kinetics and mechanisms of phase transformation is therefore of vital importance. Apart from a few cases involving crystallographic martensitic transformations, all phase transformations are mediated by diffusion. Thus, proper control and understanding of the process of diffusion during nucleation, g

  5. Drift in Diffusion Gradients

    Directory of Open Access Journals (Sweden)

    Fabio Marchesoni

    2013-08-01

    Full Text Available The longstanding problem of Brownian transport in a heterogeneous quasi one-dimensional medium with space-dependent self-diffusion coefficient is addressed in the overdamped (zero mass limit. A satisfactory mesoscopic description is obtained in the Langevin equation formalism by introducing an appropriate drift term, which depends on the system macroscopic observables, namely the diffuser concentration and current. The drift term is related to the microscopic properties of the medium. The paradoxical existence of a finite drift at zero current suggests the possibility of designing a Maxwell demon operating between two equilibrium reservoirs at the same temperature.

  6. Nonlinear diffusion equations

    CERN Document Server

    Wu Zhuo Qun; Li Hui Lai; Zhao Jun Ning

    2001-01-01

    Nonlinear diffusion equations, an important class of parabolic equations, come from a variety of diffusion phenomena which appear widely in nature. They are suggested as mathematical models of physical problems in many fields, such as filtration, phase transition, biochemistry and dynamics of biological groups. In many cases, the equations possess degeneracy or singularity. The appearance of degeneracy or singularity makes the study more involved and challenging. Many new ideas and methods have been developed to overcome the special difficulties caused by the degeneracy and singularity, which

  7. Diffusion in advanced materials

    CERN Document Server

    Murch, Graeme; Belova, Irina

    2014-01-01

    In the first chapter Prof. Kozubski and colleagues present atomisticsimulations of superstructure transformations of intermetallic nanolayers.In Chapter 2, Prof. Danielewski and colleagues discuss a formalism for themorphology of the diffusion zone in ternary alloys. In Chapter 3, ProfessorsSprengel and Koiwa discuss the classical contributions of Boltzmann andMatano for the analysis of concentration-dependent diffusion. This isfollowed by Chapter 4 by Professor Cserháti and colleagues on the use of Kirkendall porosity for fabricating hollow hemispheres. In Chapter 5,Professor Morton-Blake rep

  8. Ambipolar diffusion in plasma

    International Nuclear Information System (INIS)

    Silva, T.L. da.

    1987-01-01

    Is this thesis, a numerical method for the solution of the linear diffusion equation for a plasma containing two types of ions, with the possibility of charge exchange, has been developed. It has been shown that the decay time of the electron and ion densities is much smaller than that in a plasma containing only a single type of ion. A non-linear diffusion equation, which includes the effects of an external electric field varying linearly in time, to describe a slightly ionized plasma has also been developed. It has been verified that the decay of the electron density in the presence of such an electric field is very slow. (author)

  9. Restenosis: A Challenge to Angioplasty

    Indian Academy of Sciences (India)

    fluoroscopy, as it moves down the artery. Wherever the flow is blocked, it clearly shows up as .... animals were sacrificed at various intervals of time (weeks to months) and their arteries examined for the efficacy ... Alterna- tively, a stent implanted with a small amount of radioactive material is placed permanently at the site of ...

  10. Restenosis: A Challenge to Angioplasty

    Indian Academy of Sciences (India)

    biology. He occasionally writes popular science articles in both English and Kannada. He was also the Editor of Journal of. Medical Physics. M S S Murthy. Fatty deposits clog the coronary arteries blocking .... Unlike bone, the arteries, the blood, and the atherosclerotic plaque are transparent to X-rays and do not show up on ...

  11. Anisotropy in "isotropic diffusion" measurements due to nongaussian diffusion

    DEFF Research Database (Denmark)

    Jespersen, Sune Nørhøj; Olesen, Jonas Lynge; Ianuş, Andrada

    2017-01-01

    Designing novel diffusion-weighted NMR and MRI pulse sequences aiming to probe tissue microstructure with techniques extending beyond the conventional Stejskal-Tanner family is currently of broad interest. One such technique, multidimensional diffusion MRI, has been recently proposed to afford...... model-free decomposition of diffusion signal kurtosis into terms originating from either ensemble variance of isotropic diffusivity or microscopic diffusion anisotropy. This ability rests on the assumption that diffusion can be described as a sum of multiple Gaussian compartments, but this is often...

  12. Diffusion Based Photon Mapping

    DEFF Research Database (Denmark)

    Schjøth, Lars; Fogh Olsen, Ole; Sporring, Jon

    2007-01-01

    . To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features...

  13. Diffusion welding of metals

    International Nuclear Information System (INIS)

    Susei, Shuzo; Matsui, Shigetomo; Yamada, Takeshi

    1978-01-01

    Recently, the materials with high heat resistance, corrosion resistance or strength have been developed, and some of them cannot be welded by ordinary method. Thereupon solid phase joining method is noticed, the mechanism of which is entirely different from conventional fusion welding. Among various solid phase joining methods, diffusion welding has many features. In case of joining same material, the joint can be made chemically and mechanically same as the parent material, and in case of joining different materials, joining can be made without forming any harmful compound, and the embrittlement of joints can be avoided. Kawasaki Heavy Industries Corp. has carried out a series of research on the diffusion welding of various metals, but in this paper, the characteristics of the joints of same material and different materials in titanium alloys are reported. The diffusion welding apparatus used adopts radiation heating using a tungsten heater and a hydraulic cylinder for pressing. The atmosphere of welded materials is kept in vacuum. The tested materials were industrial pure titanium TB 35 and Ti-6 Al-4 V alloy. The weldability of these materials by diffusion welding was studied, and it was confirmed that the joint efficiency of 100% was able to be obtained. However, for the practical application, more studies are required. (Kako, I.)

  14. Bronnen van diffuse bodembelasting

    NARCIS (Netherlands)

    Lijzen JPA; Ekelenkamp A; LBG; DGM/BO

    1995-01-01

    The aim of this study was to support the policy on preventive soil protection with information on the diffuse (non-local) emissions to soil and the influence on future soil quality. This study is related to inventories on (potential) sources of local soil pollution (e.g. industrial areas,

  15. Diffusion in ceramics

    CERN Document Server

    Pelleg, Joshua

    2016-01-01

    This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. Solutions of Fick’s second law for constant D, diffusion in grain boundaries and dislocations are presented along with a look at the atomistic approach for the random motion of atoms. In the second part, the author discusses diffusion in several technologically important ceramics. The ceramics selected are monolithic single phase ones, including: A12O3, SiC, MgO, ZrO2 and Si3N4. Of these, three refer to oxide ceramics (alumina, magnesia and zirconia). Carbide based ceramics are represented by the technologically very important Si-ca...

  16. Diffusion in building wakes

    International Nuclear Information System (INIS)

    Ramsdell, J.V.

    1988-03-01

    Straight-line Gaussian models adequately describe atmospheric diffusion for many applications. They have been modified for use in estimating diffusion in building wakes by adding terms that include projected building area and by redefining the diffusion coefficients so that the coefficients have minimum values that are related to building dimensions. In a recent study, Ramsdell reviewed the building-wake dispersion models used by the Nuclear Regulatory Commission (NRC) in its control room habitability assessments. The review included comparison of model estimates of centerline concentrations with concentrations observed in experiments at seven nuclear reactors. In general, the models are conservative in that they tend to predict concentrations that are greater than those actually observed. However, the models show little skill in accounting for variations in the observed concentrations. Subsequently, the experimental data and multiples linear regression techniques have been used to develop a new building wake diffusion model. This paper describes the new building wake model and compares it with other models. 8 refs., 2 figs

  17. Osmosis and Diffusion

    Science.gov (United States)

    Sack, Jeff

    2005-01-01

    OsmoBeaker is a CD-ROM designed to enhance the learning of diffusion and osmosis by presenting interactive experimentation to the student. The software provides several computer simulations that take the student through different scenarios with cells, having different concentrations of solutes in them.

  18. Diffusion Based Photon Mapping

    DEFF Research Database (Denmark)

    Schjøth, Lars; Sporring, Jon; Fogh Olsen, Ole

    2008-01-01

    . To address this problem, we introduce a photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way, we preserve important illumination features, while...

  19. Diffusing diffusivity: a new derivation and comparison with simulations

    Indian Academy of Sciences (India)

    Rohit Jain

    Rohit Jain and K L Sebastian simulations of a tracer particle diffusing in crowded environment of randomly moving barriers,9 for dif- fusion in a 2D complex plasma10 and for activated motion in live cells.11 Recently, we12 gave a model of “diffusing diffusivity” where diffusion coefficient is modeled as a Lévy flight process ...

  20. Fractal model of anomalous diffusion.

    Science.gov (United States)

    Gmachowski, Lech

    2015-12-01

    An equation of motion is derived from fractal analysis of the Brownian particle trajectory in which the asymptotic fractal dimension of the trajectory has a required value. The formula makes it possible to calculate the time dependence of the mean square displacement for both short and long periods when the molecule diffuses anomalously. The anomalous diffusion which occurs after long periods is characterized by two variables, the transport coefficient and the anomalous diffusion exponent. An explicit formula is derived for the transport coefficient, which is related to the diffusion constant, as dependent on the Brownian step time, and the anomalous diffusion exponent. The model makes it possible to deduce anomalous diffusion properties from experimental data obtained even for short time periods and to estimate the transport coefficient in systems for which the diffusion behavior has been investigated. The results were confirmed for both sub and super-diffusion.

  1. Urban diffusion problems

    International Nuclear Information System (INIS)

    Hanna, S.R.

    1976-01-01

    It is hoped that urban diffusion models of air pollutants can eventually confidently be used to make major decisions, such as in planning the layout of a new industrial park, determining the effects of a new highway on air quality, or estimating the results of a new automobile emissions exhaust system. The urban diffusion model itself should be able to account for point, line, and area sources, and the local aerodynamic effects of street canyons and building wakes. Removal or transformations due to dry or wet deposition and chemical reactions are often important. It would be best if the model included meteorological parameters such as wind speed and temperature as dependent variables, since these parameters vary significantly when air passes from rural surfaces over urban surfaces

  2. Diffuse Ceiling Ventilation

    DEFF Research Database (Denmark)

    Zhang, Chen; Heiselberg, Per; Nielsen, Peter V.

    2014-01-01

    As a novel air distribution system, diffuse ceiling ventilation combines the suspended acoustic ceiling with ventilation supply. Due to the low-impulse supply from the large ceiling area, the system does not generate draught when supplying cold air. However, heat sources play an important role...... on thermal comfort in the occupant zone. Another characteristic of this system is its lower pressure drop compared with conventional ventilation systems, which reduces the noise problem and, at the same time, the energy consumption of the fan can be reduced. This review is based on a number of experimental...... and numerical studies on diffuse ceiling ventilation. Performance in terms of thermal comfort, air quality, pressure drop as well as radiant cooling potential are examined. Finally, a discussion on the proper design of the suspended ceiling and plenum to achieve a uniform air distribution and surface...

  3. Magnetic diffuse scattering

    International Nuclear Information System (INIS)

    Cable, J.W.

    1987-01-01

    The diffuse scattering of neutrons from magnetic materials provides unique and important information regarding the spatial correlations of the atoms and the spins. Such measurements have been extensively applied to magnetically ordered systems, such as the ferromagnetic binary alloys, for which the observed correlations describe the magnetic moment fluctuations associated with local environment effects. With the advent of polarization analysis, these techniques are increasingly being applied to study disordered paramagnetic systems such as the spin-glasses and the diluted magnetic semiconductors. The spin-pair correlations obtained are essential in understanding the exchange interactions of such systems. In this paper, we describe recent neutron diffuse scattering results on the atom-pair and spin-pair correlations in some of these disordered magnetic systems. 56 refs

  4. Diffused Religion and Prayer

    Directory of Open Access Journals (Sweden)

    Roberto Cipriani

    2011-06-01

    Full Text Available It is quite likely that the origins of prayer are to be found in ancient mourning and bereavement rites. Primeval ritual prayer was codified and handed down socially to become a deep-rooted feature of people’s cultural behavior, so much so, that it may surface again several years later, in the face of death, danger, need, even in the case of relapse from faith and religious practice. Modes of prayer depend on religious experience, on relations between personal prayer and political action, between prayer and forgiveness, and between prayer and approaches to religions. Various forms of prayer exist, from the covert-hidden to the overt-manifest kind. How can they be investigated? How can one, for instance, explore mental prayer? These issues regard the canon of diffused religion and, therefore, of diffused prayer.

  5. Building-wake diffusion

    International Nuclear Information System (INIS)

    Ramsdell, J.V.

    1988-01-01

    A recent review of building-wake diffusion models compares model predictions of centerline concentrations in building wakes with concentrations observed in experiments at seven nuclear reactors. In general, the model predictions are conservative in that they tend to predict concentrations that are greater than those actually observed. However, the models show little skill in accounting for variations in the observed concentrations. Analysis of experimental data indicates that the general form of the standard wake diffusion models is inconsistent with observed variations of concentrations in the wakes. The inconsistency is especially marked for ground-level releases. As an interim measure, multiple linear regression techniques have been used to develop a statistical building-wake model alternative to the current models. This paper describes the statistical wake model and compares it with other models

  6. Diffusion in inhomogeneous media

    Science.gov (United States)

    Donos, Aristomenis; Gauntlett, Jerome P.; Ziogas, Vaios

    2017-12-01

    We consider the transport of conserved charges in spatially inhomogeneous quantum systems with a discrete lattice symmetry. We analyze the retarded two-point functions involving the charges and the associated currents at long wavelengths, compared to the scale of the lattice, and, when the dc conductivities are finite, extract the hydrodynamic modes associated with diffusion of the charges. We show that the dispersion relations of these modes are related to the eigenvalues of a specific matrix constructed from the dc conductivities and certain thermodynamic susceptibilities, thus obtaining generalized Einstein relations. We illustrate these general results in the specific context of relativistic hydrodynamics where translation invariance is broken using spatially inhomogeneous and periodic deformations of the stress tensor and the conserved U (1 ) currents. Equivalently, this corresponds to considering hydrodynamics on a curved manifold, with a spatially periodic metric and chemical potential, and we obtain the dispersion relations for the heat and charge diffusive modes.

  7. Diffuse galactic annihilation radiation

    Science.gov (United States)

    Ramaty, R.; Lingenfelter, R. E.

    1993-01-01

    The study reports observations of positron annihilation radiation from the inner region of the Galaxy which show that there are two components of the radiation: a steady, diffuse Galactic component and a variable component from discrete, presumably compact sources. The existence of the variable component is supported by the ensemble of all narrow FOV 511 keV line observations, including recent detections with OSSE. The fit of this ensemble to a time-independent source distribution can be excluded at the approximately 3-sigma level. The same ensemble, combined with the broad FOV SMM observations of Galactic 511 keV line emission, sets constraints on the Galactic distribution of the diffuse component.

  8. Diffuse neonatal gastric infarction

    International Nuclear Information System (INIS)

    Johnson, J.F.; Woisard, K.K.; Cooper, G.L.

    1988-01-01

    Diffuse neonatal gastric infarction can be a devastating complication of invasion of the gastric wall and vessels by fungi colonizing the gastric mucosa. Even in the presence of extensive transmural necrosis, however, the radiographs do not necessarily show evidence of gastric mucosal abnormality. Instead, plain films and positive contrast studies may erroneously suggest a mechanical gastric outlet obstruction. Ancillary evidence of a devitalized viscus in a baby who appears to have complete gastric outlet obstruction should suggest the diagnosis of gastric infarction. (orig.)

  9. Diffuse neonatal gastric infarction

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, J.F.; Woisard, K.K.; Cooper, G.L.

    1988-02-01

    Diffuse neonatal gastric infarction can be a devastating complication of invasion of the gastric wall and vessels by fungi colonizing the gastric mucosa. Even in the presence of extensive transmural necrosis, however, the radiographs do not necessarily show evidence of gastric mucosal abnormality. Instead, plain films and positive contrast studies may erroneously suggest a mechanical gastric outlet obstruction. Ancillary evidence of a devitalized viscus in a baby who appears to have complete gastric outlet obstruction should suggest the diagnosis of gastric infarction.

  10. Technology diffusion and growth

    OpenAIRE

    Erzo G. J. Luttmer

    2009-01-01

    Suppose firms are subject to decreasing returns and permanent idiosyncratic productivity shocks. Suppose also firms can only stay in business by continuously paying a fixed cost. New firms can enter. Firms with a history of relatively good productivity shocks tend to survive and others are forced to exit. This paper identifies assumptions about entry that guarantee a stationary firm size distribution and lead to balanced growth. The range of technology diffusion mechanisms that can be conside...

  11. Diffusion bonding techniques

    International Nuclear Information System (INIS)

    Peters, R.D.

    1978-01-01

    The applications of diffusion bonding at the General Electric Neutron Devices Department are briefly discussed, with particular emphasis on the gold/gold or gold/indium joints made between metallized alumina ceramic parts in the vacuum switch tube and the crystal resonator programs. Fixtures which use the differential expansion of dissimilar metals are described and compared to one that uses hydraulic pressure to apply the necessary bonding force

  12. Diffusing Best Practices

    DEFF Research Database (Denmark)

    Pries-Heje, Jan; Baskerville, Richard

    2014-01-01

    Both the practice and the research literature on information systems attach great value to the identification and dissemination of information on “best practices”. In the philosophy of science, this type of knowledge is regarded as technological knowledge because it becomes manifest in the succes...... that the behavior will be effective). These two factors were especially critical if the source context of the best practice is qualitatively different from the target context into which the organization is seeking to diffuse the best practice.......Both the practice and the research literature on information systems attach great value to the identification and dissemination of information on “best practices”. In the philosophy of science, this type of knowledge is regarded as technological knowledge because it becomes manifest...... approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...

  13. The Pearson diffusions: A class of statistically tractable diffusion processes

    DEFF Research Database (Denmark)

    Forman, Julie Lyng; Sørensen, Michael

    classification is presented for the ergodic Pearson diffusions. The class of stationary distributions equals the full Pearson system of distributions. Well-known instances are the Ornstein-Uhlenbeck processes and the square root (CIR) processes. Also diffusions with heavy-tailed and skew marginals are included....... Special attention is given to a skew t-type distribution. Explicit formulae for the conditional moments and the polynomial eigenfunctions are derived. The analyti- cal tractability is inherited by transformed Pearson diffusions, integrated Pearson diffusions, sums of Pearson diffusions, and stochastic...

  14. Anisotropic light diffusion: an oxymoron?

    Science.gov (United States)

    Kienle, Alwin

    2007-05-25

    Light propagation in anisotropic random media is studied in the steady-state and time domains. Solutions of the anisotropic diffusion equation are compared to results obtained by the Monte Carlo method. Contrary to what has been reported so far, we find that even in the "diffusive regime" the anisotropic diffusion equation does not describe correctly the light propagation in anisotropic random media.

  15. Herausforderungen der Diffusion sozialer Innovationen

    NARCIS (Netherlands)

    Brandsen, T.

    2014-01-01

    Unter Rückgriff auf das Diffusions-Modell von Everett M. Rogers und mithilfe der Metapher der Übermittlung von Nachrichten zeigt der Autor auf, hinsichtlich welcher Aspekte sich die Diffusion sozialer Innovationen von der Diffusion anderer, besser erforschter Innovations- Typen im Wirtschaftssektor

  16. Particle diffusion in a spheromak

    International Nuclear Information System (INIS)

    Meyerhofer, D.D.; Levinton, F.M.; Yamada, M.

    1988-01-01

    The local carbon particle diffusion coefficient was measured in the Proto S-1/C spheromak using a test particle injection scheme. When the plasma was not in a force-free Taylor state, and when there were pressure gradients in the plasma, the particle diffusion was five times that predicted by Bohm and was consistent with collisional drift wave diffusion. The diffusion appears to be driven by correlations of the fluctuating electric field and density. During the decay phase of the discharge when the plasma was in the Taylor state, the diffusion coefficient of the carbon was classical. 23 refs., 4 figs

  17. Advanced diffusion processes and phenomena

    CERN Document Server

    Öchsner, Andreas; Belova, Irina

    2014-01-01

    This topical volume on Advanced Diffusion Processes and Phenomena addresses diffusion in a wider sense of not only mass diffusion but also heat diffusion in fluids and solids. Both diffusion phenomena play an important role in the characterization of engineering materials and corresponding structures. Understanding these different transport phenomena at many levels, from atomistic to macro, has therefore long attracted the attention of many researchers in materials science and engineering and related disciplines. The present topical volume captures a representative cross-section of some of the

  18. Diffusion in amorphous media

    Science.gov (United States)

    Iotov, Mihail S.

    The goals of this research are twofold: First, to develop methods and tools for studying problems in chemistry, material science and biology, as well as accurate prediction of the properties of structures and materials of importance to those fields. Second, use those tools to apply the methods to practical problems. In terms of methodology development this thesis focuses on two topics: One: Development of a massively parallel computer program to perform electronic, atomic, molecular levels simulations of problems in chemistry, material science and biology. This computer program uses existing and emerging hardware platforms and parallel tools and is based on decades long research in computer modeling and algorithms. We report on that development in Chapter 3. Two: Development of tools for Molecular Dynamics simulation and methods and tools for course-grained meso-scale modeling of transport properties and especially diffusion of gas penetrants in polymers. We have formulated a new method for extracting coarse-grained information from short (0.2-0.5 nanoseconds [ns]) MD simulations and use this in a meso-scale simulation to calculate diffusion constants in polymer matrices. This is a grid-based method, which calculates the average probability of each grid point of being a void and performs constrained and biased Monte Carlo (MC) dynamics to reach much longer time regimes than possible in MD. The MC method mimics the three regimes of mean square deviation (MSD) behavior seen in MD, thus accounting for the proper mobility of the voids and the compressibility of the polymer matrix. Theoretical discussions and justification for the method is presented in chapter 6. Initial results on He diffusion in a low-density polyethylene (PE) matrix are presented in chapter 7. The behavior at different temperatures follows closely the trend observed from calibrating long term MD for this particular system.

  19. The diffuse ensemble filter

    Directory of Open Access Journals (Sweden)

    X. Yang

    2009-07-01

    Full Text Available A new class of ensemble filters, called the Diffuse Ensemble Filter (DEnF, is proposed in this paper. The DEnF assumes that the forecast errors orthogonal to the first guess ensemble are uncorrelated with the latter ensemble and have infinite variance. The assumption of infinite variance corresponds to the limit of "complete lack of knowledge" and differs dramatically from the implicit assumption made in most other ensemble filters, which is that the forecast errors orthogonal to the first guess ensemble have vanishing errors. The DEnF is independent of the detailed covariances assumed in the space orthogonal to the ensemble space, and reduces to conventional ensemble square root filters when the number of ensembles exceeds the model dimension. The DEnF is well defined only in data rich regimes and involves the inversion of relatively large matrices, although this barrier might be circumvented by variational methods. Two algorithms for solving the DEnF, namely the Diffuse Ensemble Kalman Filter (DEnKF and the Diffuse Ensemble Transform Kalman Filter (DETKF, are proposed and found to give comparable results. These filters generally converge to the traditional EnKF and ETKF, respectively, when the ensemble size exceeds the model dimension. Numerical experiments demonstrate that the DEnF eliminates filter collapse, which occurs in ensemble Kalman filters for small ensemble sizes. Also, the use of the DEnF to initialize a conventional square root filter dramatically accelerates the spin-up time for convergence. However, in a perfect model scenario, the DEnF produces larger errors than ensemble square root filters that have covariance localization and inflation. For imperfect forecast models, the DEnF produces smaller errors than the ensemble square root filter with inflation. These experiments suggest that the DEnF has some advantages relative to the ensemble square root filters in the regime of small ensemble size, imperfect model, and copious

  20. Diffusion in silicon isotope heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Silvestri, Hughes Howland [Univ. of California, Berkeley, CA (United States)

    2004-01-01

    The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and 28Si enriched layers, enables the observation of 30Si self-diffusion from the natural layers into the 28Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly

  1. Diffusion or bulk flow

    DEFF Research Database (Denmark)

    Schulz, Alexander

    2015-01-01

    assimilate movement includes an apoplasmic step, this mode is called apoplasmic loading. Well established is also the polymer-trap loading mode, where the phloem-transport sugars are raffinose-family oligomers in herbaceous plants. Also this mode depends on the investment of energy, here for sugar...... is currently matter of discussion, called passive symplasmic loading. Based on the limited material available, this review compares the different loading modes and suggests that diffusion is the driving force in apoplasmic loaders, while bulk flow plays an increasing role in plants having a continuous...

  2. Inhibition of neointima formation by local delivery of estrogen receptor alpha and beta specific agonists

    NARCIS (Netherlands)

    Krom, Y.D.; Pires, N.M.M.; Jukema, J.W.; Vries, M.R. de; Frants, R.R.; Havekes, L.M.; Dijk, K.W. van; Quax, P.H.A.

    2007-01-01

    Objective: Neointima formation is the underlying mechanism of (in-stent) restenosis. 17β-Estradiol (E2) is known to inhibit injury-induced neointima formation and post-angioplasty restenosis. Estrogen receptor alpha (ERα) has been demonstrated to mediate E2 anti-restenotic properties. However, the

  3. Microvascular denudation of the femoral artery of the mouse as a model for restenosis; Mikrovaskulaere Denudation der Arteria femoralis der Maus - ein Restenosemodell fuer die Experimentelle Radiologie

    Energy Technology Data Exchange (ETDEWEB)

    Feuls, R.; Bantleon, R.; Henning, E.B.; Tepe, G.; Khorchidi, S.; Reis, E.D.; Duda, S.H. [Eberhard-Karls-Univ. Tuebingen, Abteilung fuer Radiologische Diagnostik (Germany); Chereshnev, I. [Mount Sinai School of Medicine, Department of Surgery, New York City (United States)

    2003-07-01

    Objective: To present technique and results of a microvascular denudation of the common femoral artery of the mouse as a model for inducing intimal hyperplasia in interventional radiology. Materials and methods: Under general anesthesia introduced by intraperitoneal injection, 14 B6129F1 hybrid mice (7 females and 7 males) at a mean age of 12.1{+-}1.8 weeks and a mean weight of 28{+-}2.8 grams had a groin incision of the vascular bundle directly distal to the inguinal ligament in preparation of placing a vascular clamp. Thereafter, the femoral artery was dissected distal to the origin of the epigastric artery and a loop prepared for a ligation proximal to the planned arteriotomy. Through an arteriotomy performed free-hand with a pair of micro scissors, a 0.010'' (=0.25 mm) guidewire was introduced into the vessel and advanced to the aortic bifurcation. The guidewire was moved back and forth three times. The same procedure was performed on the other side as sham-operation, i.e., without introduction and passage of a guidewire. The resulting changes of the vessel wall were evaluated by histology and morphometry. Results: Four weeks after intervention, the mean intima-to-media-ratio (IMR) was 1.80{+-}0.28. A significant difference was observed between the sexes, with an IMR of 1.41{+-}0.29 in females and an IMR of 2.24{+-}0.45 in males (p=0.0173). The neointima led to an overall luminal loss of 50.2%{+-}8.3% without significant sex difference (p=0.09), but the average lumina loss was still more severe in females, amounting to 43.9% in comparison to 56.1% in males. This technique induces a significant neointima formation in a reproducible manner. The internal elastic membrane was preserved in all vessels. Conclusion: This technique is an excellent model to examine the differences between genetically modified mice to clarify the role of putative key molecules in the pathophysiology of restenosis. (orig.) [German] Ziel: Wir moechten Technik und Ergebnisse der

  4. Diffusion in Solids Fundamentals, Methods, Materials, Diffusion-Controlled Processes

    CERN Document Server

    Mehrer, Helmut

    2007-01-01

    Diffusion is a vital topic in solid-state physics and chemistry, physical metallurgy and materials science. Diffusion processes are ubiquitous in solids at elevated temperatures. A thorough understanding of diffusion in materials is crucial for materials development and engineering. This book first gives an account of the central aspects of diffusion in solids, for which the necessary background is a course in solid state physics. It then provides easy access to important information about diffuson in metals, alloys, semiconductors, ion-conducting materials, glasses and nanomaterials. Several diffusion-controlled phenomena, including ionic conduction, grain-boundary and dislocation pipe diffusion, are considered as well. Graduate students in solid-state physics, physical metallurgy, materials science, physical and inorganic chemistry or geophysics will benefit from this book as will physicists, chemists, metallurgists, materials engineers in academic and industrial research laboratories.

  5. Apparatus for diffusion separation

    International Nuclear Information System (INIS)

    Nierenberg, W.A.

    1976-01-01

    A diffuser separator apparatus is described which comprises a plurality of flow channels in a single stage. Each of said channels has an inlet port and an outlet port and a constant cross sectional area between said ports. At least a portion of the defining surface of each of said channels is a diffusion separation membrane, and each of said channels is a different cross sectional area. Means are provided for connecting said channels in series so that each successive channel of said series has a smaller cross sectional area than the previous channel of said series. Also provided are a source of gaseous mixture, individual means for flowing said gaseous mixture to the inlet port of each of said channels, gas receiving and analyzing means, individual means for flowing gas passing from each of said outlet ports and means for flowing gas passing through said membranes to said receiving and analyzing means, and individual means for connecting the outlet port of each channel with the inlet port of the channel having the next smaller cross sectional area

  6. Apoplastic Diffusion Barriers in Arabidopsis

    Science.gov (United States)

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  7. Light diffusing fiber optic chamber

    Science.gov (United States)

    Maitland, Duncan J.

    2002-01-01

    A light diffusion system for transmitting light to a target area. The light is transmitted in a direction from a proximal end to a distal end by an optical fiber. A diffusing chamber is operatively connected to the optical fiber for transmitting the light from the proximal end to the distal end and transmitting said light to said target area. A plug is operatively connected to the diffusing chamber for increasing the light that is transmitted to the target area.

  8. Confinement and diffusion in tokamaks

    International Nuclear Information System (INIS)

    McWilliams, R.

    1988-01-01

    The effect of electric field fluctuations on confinement and diffusion in tokamak is discussed. Based on the experimentally determined cross-field turbolent diffusion coefficient, D∼3.7*cT e /eB(δn i /n i ) rms which is also derived by a simple theory, the cross-field diffusion time, tp=a 2 /D, is calculated and compared to experimental results from 51 tokamak for standard Ohmic operation

  9. Fractal model of anomalous diffusion

    OpenAIRE

    Gmachowski, Lech

    2015-01-01

    An equation of motion is derived from fractal analysis of the Brownian particle trajectory in which the asymptotic fractal dimension of the trajectory has a required value. The formula makes it possible to calculate the time dependence of the mean square displacement for both short and long periods when the molecule diffuses anomalously. The anomalous diffusion which occurs after long periods is characterized by two variables, the transport coefficient and the anomalous diffusion exponent. An...

  10. Nonlocal diffusion and applications

    CERN Document Server

    Bucur, Claudia

    2016-01-01

    Working in the fractional Laplace framework, this book provides models and theorems related to nonlocal diffusion phenomena. In addition to a simple probabilistic interpretation, some applications to water waves, crystal dislocations, nonlocal phase transitions, nonlocal minimal surfaces and Schrödinger equations are given. Furthermore, an example of an s-harmonic function, its harmonic extension and some insight into a fractional version of a classical conjecture due to De Giorgi are presented. Although the aim is primarily to gather some introductory material concerning applications of the fractional Laplacian, some of the proofs and results are new. The work is entirely self-contained, and readers who wish to pursue related subjects of interest are invited to consult the rich bibliography for guidance.

  11. Diffuse parenchymal lung disease

    Directory of Open Access Journals (Sweden)

    Sara Tomassetti

    2017-04-01

    Full Text Available Between September 2015 and August 2016 there were >1500 publications in the field of diffuse parenchymal lung diseases (DPLDs. For the Clinical Year in Review session at the European Respiratory Society Congress that was held in London, UK, in September 2016, we selected only five articles. This selection, made from the enormous number of published papers, does not include all the relevant studies that will significantly impact our knowledge in the field of DPLDs in the near future. This review article provides our personal view on the following topics: early diagnosis of idiopathic pulmonary fibrosis, current knowledge on the multidisciplinary team diagnosis of DPLDs and the diagnostic role of transbronchial cryobiopsy in this diagnostic setting, insights on the new entity of interstitial pneumonia with autoimmune features, and new therapeutic approaches for scleroderma-related interstitial lung disease.

  12. Hereditary diffuse gastric cancer

    DEFF Research Database (Denmark)

    van der Post, Rachel S; Vogelaar, Ingrid P; Carneiro, Fátima

    2015-01-01

    Germline CDH1 mutations confer a high lifetime risk of developing diffuse gastric (DGC) and lobular breast cancer (LBC). A multidisciplinary workshop was organised to discuss genetic testing, surgery, surveillance strategies, pathology reporting and the patient's perspective on multiple aspects......, including diet post gastrectomy. The updated guidelines include revised CDH1 testing criteria (taking into account first-degree and second-degree relatives): (1) families with two or more patients with gastric cancer at any age, one confirmed DGC; (2) individuals with DGC before the age of 40 and (3...... the high mortality associated with invasive disease, prophylactic total gastrectomy at a centre of expertise is advised for individuals with pathogenic CDH1 mutations. Breast cancer surveillance with annual breast MRI starting at age 30 for women with a CDH1 mutation is recommended. Standardised endoscopic...

  13. Diffuse scattering in Ih ice

    International Nuclear Information System (INIS)

    Wehinger, Björn; Krisch, Michael; Bosak, Alexeï; Chernyshov, Dmitry; Bulat, Sergey; Ezhov, Victor

    2014-01-01

    Single crystals of ice Ih, extracted from the subglacial Lake Vostok accretion ice layer (3621 m depth) were investigated by means of diffuse x-ray scattering and inelastic x-ray scattering. The diffuse scattering was identified as mainly inelastic and rationalized in the frame of ab initio calculations for the ordered ice XI approximant. Together with Monte-Carlo modelling, our data allowed reconsidering previously available neutron diffuse scattering data of heavy ice as the sum of thermal diffuse scattering and static disorder contribution. (paper)

  14. Diffusing diffusivity: a new derivation and comparison with simulations

    Indian Academy of Sciences (India)

    Rohit Jain

    Special Issue on THEORETICAL CHEMISTRY/CHEMICAL DYNAMICS. Diffusing diffusivity: a new derivation and comparison with simulations. †. ROHIT JAINa and K L SEBASTIANa,b,∗. aDepartment of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, Karnataka 560 012,. India. bIndian Institute of ...

  15. Turing instability in reaction-diffusion systems with nonlinear diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Zemskov, E. P., E-mail: zemskov@ccas.ru [Russian Academy of Sciences, Dorodnicyn Computing Center (Russian Federation)

    2013-10-15

    The Turing instability is studied in two-component reaction-diffusion systems with nonlinear diffusion terms, and the regions in parametric space where Turing patterns can form are determined. The boundaries between super- and subcritical bifurcations are found. Calculations are performed for one-dimensional brusselator and oregonator models.

  16. Clinical outcomes of secondary gastroduodenal self-expandable metallic stent placement by stent-in-stent technique for malignant gastric outlet obstruction.

    Science.gov (United States)

    Sasaki, Takashi; Isayama, Hiroyuki; Nakai, Yousuke; Takahara, Naminatsu; Hamada, Tsuyoshi; Mizuno, Suguru; Mohri, Dai; Yagioka, Hiroshi; Kogure, Hirofumi; Arizumi, Toshihiko; Togawa, Osamu; Matsubara, Saburo; Ito, Yukiko; Yamamoto, Natsuyo; Sasahira, Naoki; Hirano, Kenji; Toda, Nobuo; Tada, Minoru; Koike, Kazuhiko

    2015-01-01

    To evaluate the efficacy and safety of secondary gastroduodenal stent placement after first stent dysfunction for malignant gastric outlet obstruction. We conducted a retrospective analysis to investigate the efficacy and safety of secondary stent-in-stent gastroduodenal stent placement. Among 260 patients who had been treated with first gastroduodenal stent placement for malignant gastric outlet obstruction, 29 patients (11.2%) were treated with secondary gastroduodenal stent placement because of first stent dysfunction. Pancreatic cancer was the major primary cancer (55.2%). A WallFlex duodenal stent was the most frequently inserted stent both as a first stent (75.9%) and as a secondary stent (62.1%). There were 22 patients (75.9%) that received gastroduodenal stents at the bending site (supraduodenal angle or infraduodenal angle). Technical and clinical success rates were 100% and 86.2%, respectively. Median eating period was 3.0 months, and median survival time was 3.5 months. As for related complications, gastrointestinal perforation, insufficient stent expansion, tumor ingrowth, tumor overgrowth, and cholangitis were experienced in 13.8% (four cases), 6.9% (two cases), 6.9% (two cases), 3.4% (one case), and 3.4% (one case), respectively. Secondary gastroduodenal stent placement might be effective for managing first stent dysfunction in malignant gastric outlet obstruction. However, gastrointestinal perforation was the major complication. © 2014 The Authors. Digestive Endoscopy © 2014 Japan Gastroenterological Endoscopy Society.

  17. Reliability of mechanical and phased-array designs for serial intravascular ultrasound examinations--animal and clinical studies in stented and non-stented coronary arteries.

    Science.gov (United States)

    Tardif, J C; Bertrand, O F; Mongrain, R; Lespérance, J; Grégoire, J; Paiement, P; Bonan, R

    2000-10-01

    Both mechanical and multi-element intravascular ultrasound designs have potential advantages and limitations that may impact on their value for clinical and research purposes. Determination of the reproducibility of measurements is critical before a given system can be used in studies such as regression of atherosclerosis trials. We performed serial intravascular ultrasound imaging with catheters using mechanical and phased-array designs in stented and non-stented coronary arteries in dogs and in patients. Both systems correlated well for areas (r > or = 0.90, p or = 0.84. p mechanical designs for measurements of area (mean difference in dogs and in patients: -0.24 and 0.96 mm2, p mechanical system (r > or = 0.96 for all measurements). The differences in absolute and relative variability between the mechanical and phased-array designs, both for reanalysis of same frames and serial pullbacks, were very small. Although multi-element and mechanical intravascular ultrasound designs are not strictly interchangeable, their similar reproducibility and the small differences in measurements demonstrate that both designs are acceptable alternatives for trials of regression of atherosclerosis. Determination of the variability for serial pullbacks of both designs was also important to assess the statistical power of such trials.

  18. Diffusion measurements by Raman spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Shapiro, Alexander; Berg, Rolf W.

    Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt......Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt...

  19. Gas Diffusion in the CNS.

    Science.gov (United States)

    Rodriguez-Grande, Beatriz; Konsman, Jan-Pieter

    2018-02-01

    Gases have been long known to have essential physiological functions in the CNS such as respiration or regulation of vascular tone. Since gases have been classically considered to freely diffuse, research in gas biology has so far focused on mechanisms of gas synthesis and gas reactivity, rather than gas diffusion and transport. However, the discovery of gas pores during the last two decades and the characterization of diverse diffusion patterns through different membranes has raised the possibility that modulation of gas diffusion is also a physiologically relevant parameter. Here we review the means of gas movement into and within the brain through "free" diffusion and gas pores, notably aquaporins, discussing the role that gas diffusion may play in the modulation of gas function. We highlight how diffusion is relevant to neuronal signaling, volume transmission, and cerebrovascular control in the case of NO, one of the most extensively studied gases. We point out how facilitated transport can be especially relevant for gases with low permeability in lipid membranes like NH 3 and discuss the possible implications of NH 3 -permeable channels in physiology and hyperammonemic encephalopathy. We identify novel research questions about how modulation of gas diffusion could intervene in CNS pathologies. This emerging area of research can provide novel and interesting insights in the field of gas biology. © 2017 Wiley Periodicals, Inc.

  20. Diffusion inside living human cells

    DEFF Research Database (Denmark)

    Leijnse, N.; Jeon, J. -H.; Loft, Steffen

    2012-01-01

    Naturally occurring lipid granules diffuse in the cytoplasm and can be used as tracers to map out the viscoelastic landscape inside living cells. Using optical trapping and single particle tracking we found that lipid granules exhibit anomalous diffusion inside human umbilical vein endothelial...

  1. Osmosis and Diffusion Conceptual Assessment

    Science.gov (United States)

    Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts

    2011-01-01

    Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified…

  2. Teaching Diffusion with a Coin

    Science.gov (United States)

    Haddad, Hamilton; Baldo, Marcus Vinicius Chrysostomo

    2010-01-01

    In this article, the authors describe an inexpensive and simple way to make students intuitively experience the probabilistic nature and nonorientated motion of diffusing particles. This understanding allows students to realize why diffusion works so well over short distances and becomes increasingly and rapidly less effective as the distances…

  3. The diffusion of constitutional rights

    NARCIS (Netherlands)

    Goderis, B.V.G.; Versteeg, M.

    Constitutions are commonly regarded as uniquely national products, shaped by domestic ideals and politics. This paper develops and empirically investigates a novel hypothesis, which is that constitutions are also shaped by transnational influence, or “diffusion.” Constitutional rights can diffuse

  4. Enhancement of diffusers BRDF accuracy

    Science.gov (United States)

    Otter, Gerard; Bazalgette Courrèges-Lacoste, Gregory; van Brug, Hedser; Schaarsberg, Jos Groote; Delwart, Steven; del Bello, Umberto

    2017-11-01

    This paper reports the result of an ESA study conducted at TNO to investigate properties of various diffusers. Diffusers are widely used in space instruments as part of the on-board absolute calibration. Knowledge of the behaviour of the diffuser is therefore most important. From measurements of launched instruments in-orbit it has been discovered that when a diffuser is used in the vacuum of space the BRDF can change with respect to the one in ambient conditions. This is called the air/vacuum effect and has been simulated in this study by measuring the BRDF in a laboratory in ambient as well as vacuum conditions. Another studied effect is related to the design parameters of the optical system and the scattering properties of the diffuser. The effect is called Spectral Features and is a noise like structure superimposed on the diffuser BRDF. Modern space spectrometers, which have high spectral resolution and/or a small field of view (high spatial resolution) are suffering from this effect. The choice of diffuser can be very critical with respect to the required absolute radiometric calibration of an instrument. Even if the Spectral Features are small it can influence the error budget of the retrieval algorithms for the level 2 products. in this presentation diffuser trade-off results are presented and the Spectral Features model applied to the optical configuration of the MERIS instrument is compared to in-flight measurements of MERIS.

  5. Ammonia diffusion through Nalophan™ bags.

    Science.gov (United States)

    Sironi, Selena; Eusebio, Lidia; Dentoni, Licinia; Capelli, Laura; Del Rosso, Renato

    2014-01-01

    The aim of the work is to verify the diffusion rate of ammonia through the Nalophan™ film that constitutes the sampling bag, considering storage times ranging from 1 to 26 h. The ammonia decay over time was evaluated using gas-chromatography for the quantification of ammonia concentration inside the bag. The research assesses the roles of both of ammonia and water concentration gradients at the polymeric film interface on the diffusion process. The results show that both the ammonia concentration gradient and, in a less pronounced way, the water concentration gradient are the main 'engines' of ammonia diffusion. Double bags seem to represent a simple solution for preventing ammonia losses during storage. Another interesting result concerns the role of the bag surface on the ammonia diffusion rate: the higher the surface/volume (S/V) ratio, the higher the ammonia diffusion rate through the polymeric film.

  6. Diffusion of childbearing within cohabitation.

    Science.gov (United States)

    Vitali, Agnese; Aassve, Arnstein; Lappegård, Trude

    2015-04-01

    The article analyzes the diffusion of childbearing within cohabitation in Norway, using municipality data over a 24-year period (1988-2011). Research has found substantial spatial heterogeneity in this phenomenon but also substantial spatial correlation, and the prevalence of childbearing within cohabitation has increased significantly over time. We consider several theoretical perspectives and implement a spatial panel model that allows accounting for autocorrelation not only on the dependent variable but also on key explanatory variables, and hence identifies the key determinants of diffusion of childbearing within cohabitation across space and over time. We find only partial support for the second demographic transition as a theory able to explain the diffusion of childbearing within cohabitation. Our results show that at least in the first phase of the diffusion (1988-1997), economic difficulties as measured by increased unemployment among men contributed to the diffusion of childbearing within cohabitation. However, the most important driver for childbearing within cohabitation is expansion in education for women.

  7. Sodium diffusion in boroaluminosilicate glasses

    DEFF Research Database (Denmark)

    Smedskjaer, Morten M.; Zheng, Qiuju; Mauro, John C.

    2011-01-01

    of isothermal sodium diffusion in BAS glasses by ion exchange, inward diffusion, and tracer diffusion experiments. By varying the [SiO2]/[Al2O3] ratio of the glasses, different structural regimes of sodium behavior are accessed. We show that the mobility of the sodium ions decreases with increasing [SiO2]/[Al2O......3] ratio, revealing that sodium is more mobile when it acts as a charge compensator to stabilize network formers than when it acts as a creator of non-bridging oxygens on tetrahedrally-coordinated silicon and trigonal boron. The impacts of both the addition of iron and its redox state on the sodium...... be attributed to the fact that for sodium inward diffusion, the charge compensation for electron holes is a rather slow process that limits the rate of diffusion. (C) 2011 Elsevier B.V. All rights reserved....

  8. Protein diffusion in polyelectrolyte solutions

    Science.gov (United States)

    Khandai, Santripti; Jena, Sidhartha S.

    2012-06-01

    The diffusion of green fluorescent protein (GFP) in non-dilute polyelectrolyte solutions of Poly-L-lysine was studied using fluorescence recovery after photobleaching (FRAP) technique. The effect of background charges on probe diffusion of GFP was studied with varying ionic strength of the solution. With increase in polyelectrolyte concentration, increase in solution viscosity and decrease in probe diffusion coefficient was observed. At the same time, we observed the diffusion coefficient increased with increase in salt concentration, while solution viscosity decreased, indicating a competition between electrostatic force between background and probe and viscosity drag. When the probe diffusion coefficient was compared with the predicted Stokes-Einstein (S-E) relation, strong positive deviations were observed for all the solutions with highest deviation observed for solution with zero salt concentration.

  9. Addimer diffusions on Si(100)

    International Nuclear Information System (INIS)

    Lee, Gun Do; Wang, C. Z.; Lu, Z. Y.; Ho, K. M.

    1999-01-01

    The diffusion pathways along the trough and between the trough and the dimer row on the Si(100) surface are investigated by tight-binding molecular dynamics calculations using the environment dependent tight-binding silicon potential and by ab initio calculations using the Car-Parrinello method. The studies discover new diffusion pathways consisting of rotation of addimer. The calculated energy barrier are in excellent agreement with experiment. The rotational diffusion pathway between the trough and the dimer row is much more energetically favorable than other diffusion pathways by parallel and perpendicular addimer. The new pathway along the trough is nearly same as the energy barrier of the diffusion pathway by dissociation of the addimer

  10. Lithium diffusion in silicate melts

    Science.gov (United States)

    Cunningham, G. J.; Henderson, P.; Lowry, R. K.; Nolan, J.; Reed, S. J. B.; Long, J. V. P.

    1983-10-01

    The diffusion properties of Li in an andesitic and pitchstone melt have been determined over the temperature range 1300-1400°C. The diffusion data have been fitted to an Arrhenius relationship between log D0 and 1/ T, and give relatively small activation energies of diffusion: 21.4±5.8 kcal mol -1 in the andesite and 20.1±2.8 kcal mol -1 in the pitchstone. Li +, unlike several other cations, shows similar diffusivities in these melt compositions to that in a basaltic melt. Despite the similar ionic radius of Li + to that of Co 2+, the diffusion properties of the two ions are very different from each other.

  11. The magnetic diffusion of neutrons; La diffusion magnetique des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, W.C. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    The purpose of this report is to examine briefly the diffusion of neutrons by substances, particularly by crystals containing permanent atomic or ionic magnetic moments. In other words we shall deal with ferromagnetic, antiferromagnetic, ferrimagnetic or paramagnetic crystals, but first it is necessary to touch on nuclear diffusion of neutrons. We shall start with the interaction of the neutron with a single diffusion centre; the results will then be applied to the magnetic interactions of the neutron with the satellite electrons of the atom; finally we shall discuss the diffusion of neutrons by crystals. (author) [French] Le but de ce rapport est d'examiner, brievement, la diffusion des neutrons par les substances, et surtout, par des cristaux qui contiennent des moments magnetiques atomiques ou ioniques permanents. C'est-a-dire que nous nous interesserons aux cristaux ferromagnetiques, antiferromagnetiques, ferrimagnetiques ou paramagnetiques; il nous faut cependant rappeler d'abord la diffusion nucleaire des neutrons. Nous commencerons par l'interaction du neutron avec un seul centre diffuseur; puis les resultats seront appliques aux interactions magnetiques du neutron avec les electrons satellites de l'atome; enfin nous discuterons la diffusion des neutrons par les cristaux. (auteur)

  12. Diffusion in membranes: Toward a two-dimensional diffusion map

    Directory of Open Access Journals (Sweden)

    Toppozini Laura

    2015-01-01

    Full Text Available For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.

  13. Multidimensional diffusion processes

    CERN Document Server

    Stroock, Daniel W

    1997-01-01

    From the reviews: "… Both the Markov-process approach and the Itô approach … have been immensely successful in diffusion theory. The Stroock-Varadhan book, developed from the historic 1969 papers by its authors, presents the martingale-problem approach as a more powerful - and, in certain regards, more intrinsic-means of studying the foundations of the subject. […] … the authors make the uncompromising decision not "to proselytise by intimidating the reader with myriad examples demonstrating the full scope of the techniques", but rather to persuade the reader "with a careful treatment of just one problem to which they apply". […] Most of the main tools of stochastic-processes theory are used, ..but it is the formidable combination of probability theory with analysis … which is the core of the work. […] I have emphasized the great importance of the Stroock-Varadhan book. It contains a lot more than I have indicated; in particular, its many exercises conain much interesting material. For immediat...

  14. Diffusive instabilities in hyperbolic reaction-diffusion equations

    Science.gov (United States)

    Zemskov, Evgeny P.; Horsthemke, Werner

    2016-03-01

    We investigate two-variable reaction-diffusion systems of the hyperbolic type. A linear stability analysis is performed, and the conditions for diffusion-driven instabilities are derived. Two basic types of eigenvalues, real and complex, are described. Dispersion curves for both types of eigenvalues are plotted and their behavior is analyzed. The real case is related to the Turing instability, and the complex one corresponds to the wave instability. We emphasize the interesting feature that the wave instability in the hyperbolic equations occurs in two-variable systems, whereas in the parabolic case one needs three reaction-diffusion equations.

  15. Diffusion tensor optical coherence tomography

    Science.gov (United States)

    Marks, Daniel L.; Blackmon, Richard L.; Oldenburg, Amy L.

    2018-01-01

    In situ measurements of diffusive particle transport provide insight into tissue architecture, drug delivery, and cellular function. Analogous to diffusion-tensor magnetic resonance imaging (DT-MRI), where the anisotropic diffusion of water molecules is mapped on the millimeter scale to elucidate the fibrous structure of tissue, here we propose diffusion-tensor optical coherence tomography (DT-OCT) for measuring directional diffusivity and flow of optically scattering particles within tissue. Because DT-OCT is sensitive to the sub-resolution motion of Brownian particles as they are constrained by tissue macromolecules, it has the potential to quantify nanoporous anisotropic tissue structure at micrometer resolution as relevant to extracellular matrices, neurons, and capillaries. Here we derive the principles of DT-OCT, relating the detected optical signal from a minimum of six probe beams with the six unique diffusion tensor and three flow vector components. The optimal geometry of the probe beams is determined given a finite numerical aperture, and a high-speed hardware implementation is proposed. Finally, Monte Carlo simulations are employed to assess the ability of the proposed DT-OCT system to quantify anisotropic diffusion of nanoparticles in a collagen matrix, an extracellular constituent that is known to become highly aligned during tumor development.

  16. Diffusion of terbium in silicon

    International Nuclear Information System (INIS)

    Nazyrov, D.Eh.

    2006-01-01

    The diffusion of terbium in silicon is studied by tracer technique in the temperature range 1100-1250 deg C. The diffusion coefficient of terbium, D Tb , is shown to increase with temperature from 4 x 10 -14 to 10 -12 cm 2 /s. The temperature dependence of D Tb at temperatures studied obeys the Arrhenius law according to: D Tb [cm 2 /s] = 5 x 10 -2 exp(-3.3 eV/kT). Experimental data on D Tb and activation energy (E a = 3.3 eV) suggest that terbium dopant diffuses in silicon along the crystal lattice nodes [ru

  17. Spin diffusion in Fermi gases

    DEFF Research Database (Denmark)

    Bruun, Georg

    2011-01-01

    We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures......, strong correlation effects are included through the Landau parameters which we extract from Monte Carlo results. We show that the spin diffusion coefficient has a minimum for a temperature somewhat below the Fermi temperature with a value that approaches the quantum limit ~/m in the unitarity regime...

  18. Accuracy of multislice CT angiography for the assessment of in-stent restenoses in the iliac arteries at reduced dose: a phantom study.

    Science.gov (United States)

    Perisinakis, K; Manousaki, E; Zourari, K; Tsetis, D; Tzedakis, A; Papadakis, A; Karantanas, A; Damilakis, J

    2011-03-01

    We investigated the potential of low-dose CT angiography for accurate assessment of in-stent restenoses (ISRs) of the iliac artery. A Rando anthropomorphic phantom (Alderson Research Labs, Stanford, CA), custom-made wax simulating hyperplastic tissue and a nitinol stent were used to simulate a patient with clinically relevant iliac artery ISRs. The cylindrical lumen was filled with a solution of iodine contrast medium diluted in saline, representing a patient's blood during CT angiography. The phantom was subjected to standard- and low-dose angiographic exposures using a modern multidetector (MD) CT scanner. The percentage of ISR was determined using the profile along a line normal to the lumen axis on reconstructed images of 2 and 5 mm slice thickness. Percentage ISRs derived using the standard- and low-dose protocols were compared. In a preliminary study, seven patients with stents were subjected to standard- and low-dose MDCT angiography during follow-up. The resulting images were assessed and compared by two experienced radiologists. The accuracy in measuring the percentage ISR was found to be better than 12% for all simulated stenoses. The differences between percentage ISRs measured on images obtained at 120 kVp/160 mAs and 80 kVp/80 mAs were below 6%. Patient image sets acquired using low-exposure factors were judged to be of satisfactory diagnostic quality. The assessment of ISR did not differ significantly between image sets acquired using the standard factors and those acquired using the low-exposure factors, although the mean reduction in patient effective dose was 48%. A reduction in exposure factors during MDCT angiography of the iliac artery is possible without affecting the accuracy in the determination of ISRs.

  19. Prevention of Intracranial In-stent Restenoses: Predilatation with a Drug Eluting Balloon, Followed by the Deployment of a Self-Expanding Stent

    International Nuclear Information System (INIS)

    Vajda, Zsolt; Güthe, Thomas; Perez, Marta Aguilar; Kurre, Wiebke; Schmid, Elisabeth; Bäzner, Hansjörg; Henkes, Hans

    2013-01-01

    Stenting in intracranial atherosclerotic disease (ICAD) is increasingly debated, due to issues of procedural safety, technical efficacy, and in-stent recurrent stenoses (ISR). In the present study, feasibility, safety, and efficacy of angioplasty using a drug-eluting balloon (DEB) followed by the implantation of a self-expanding stent (Enterprise) were evaluated for the treatment of ICAD lesions. Fifty-two patients (median age: 71 years; range: 54–86 years; male/female ratio 37:15) underwent stenting of high-grade ICAD lesions between February 2010 and November 2011 in a single center. Angioplasty using a paclitaxel coated SeQuent Please (B. Braun, Germany) or DIOR (Eurocor, Germany) coronary PTCA balloon, followed by the implantation of a self-expanding stent (Enterprise, Codman, USA) was performed in 54 lesions. Angiographic and clinical follow-up was performed at 6 and 12 weeks, 6 and 12 months, and yearly thereafter. Technical success rate, periprocedural complications, occurrence of recurrent ischemic symptoms, and the development of an ISR were analyzed. Angioplasty using a DEB followed by stent implantation was successfully performed in 44 (81 %) cases. DEB insertion failed in 19 % of the cases and angioplasty was finally performed using a conventional PTCA balloon. The combined procedure related permanent neurologic morbidity and mortality rate (stroke, ICH, and subarachnoid hemorrhage) at 30 days and beyond was 5 %. Angiographic and clinical follow-up were obtained in 33 (61 %) lesions in 32 patients. Recurrent stenosis was seen in one (3 %) lesion. Angioplasty and stenting using a DEB is safe and yields encouragingly low ISR rates. Further technical developments to improve lesion accessibility are, nevertheless, mandatory.

  20. Improved diffuser for augmenting a wind turbine

    Science.gov (United States)

    Foreman, K.M.; Gilbert, B.L.

    A diffuser for augmenting a wind turbine having means for energizing the boundary layer at several locations along the diffuser walls is improved by the addition of a short collar extending radially outward from the outlet of the diffuser.

  1. Dual role of circulating endothelial progenitor cells in stent struts endothelialisation and neointimal regrowth: A substudy of the IN-PACT CORO trial

    Energy Technology Data Exchange (ETDEWEB)

    De Maria, Giovanni Luigi [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy); Porto, Italo, E-mail: italo.porto@gmail.com [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy); Interventional Cardiology Unit, San Donato Hospital, Arezzo (Italy); Burzotta, Francesco; Brancati, Marta Francesca; Trani, Carlo; Pirozzolo, Giancarlo; Leone, Antonio Maria; Niccoli, Giampaolo [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy); Prati, Francesco [Department of Interventional Cardiology, San Giovanni Hospital, Rome (Italy); Crea, Filippo [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy)

    2015-01-15

    higher neointimal volume and a lower rate of uncovered struts at six months of follow up are significantly associated to higher baseline levels of endothelial progenitor cells (EPC) • Baseline EPC level is an independent predictor of neointimal volume and struts coverage rate at six months of follow up. • At the same, the detection of higher neointimal volume in those patients with persistent high EPC levels at follow up suggests the possible involvement of these elements in an exaggerated healing answer to stent-related injury leading to instent restenosis.

  2. Diffusion-Exchange Weighted Imaging

    Directory of Open Access Journals (Sweden)

    Saadallah Ramadan

    2009-01-01

    Full Text Available A method has been developed whereby diffusion and exchange in micro cellular structures in the human brain are correlated to produce a new type of image contrast leading to determination of water exchange rates in vivo. The diffusion method relies on differential apparent diffusion coefficients as detectable nuclei exchange between adjacent compartments marked with different apparent diffusion coefficient values (e.g. intra- and extra-cellular compartments. A new pulse sequence was developed, and used to calculate water intra/extra mean residence times in brain, and the signal dependence on various experimental parameters was analysed. The method was tested in vivo at 3T field strength and produced 160 ms and 550 ms for extra-cellular and intra-cellular mean residence times, respectively.

  3. Simulation of multivariate diffusion bridges

    DEFF Research Database (Denmark)

    Bladt, Mogens; Finch, Samuel; Sørensen, Michael

    We propose simple methods for multivariate diffusion bridge simulation, which plays a fundamental role in simulation-based likelihood and Bayesian inference for stochastic differential equations. By a novel application of classical coupling methods, the new approach generalizes a previously...... proposed simulation method for one-dimensional bridges to the mulit-variate setting. First a method of simulating approzimate, but often very accurate, diffusion bridges is proposed. These approximate bridges are used as proposal for easily implementable MCMC algorithms that produce exact diffusion bridges....... The new method is much more generally applicable than previous methods. Another advantage is that the new method works well for diffusion bridges in long intervals because the computational complexity of the method is linear in the length of the interval. In a simulation study the new method performs well...

  4. Atmospheric turbulence and diffusion research

    International Nuclear Information System (INIS)

    Hosker, R.P. Jr.

    1993-01-01

    The Atmospheric Turbulence and Diffusion Division (well known in the atmospheric dispersion community as the Atmospheric Turbulence and Diffusion Laboratory, ATDL) is one of several field facilities of NOAAs Air Resources Laboratory, headquartered in Silver Spring, Maryland. The laboratory conducts research on matters of atmospheric diffusion and turbulent exchange, concerning air quality. ATDD focuses attention on the physics of the lower atmosphere, with special emphasis on the processes contributing to atmospheric transport, dispersion, deposition, and air-surface exchange, and on the development of predictive capabilities using the results of this research. Research is directed toward issues of national and global importance related to the missions of DOE, to DOE's Oak Ridge Field Office, and to NOAA. The program is divided into four major projects: plume transport and diffusion in the planetary boundary layer, complex topography, canopy micrometeorology, and air-surface exchange

  5. Kurtosis as a diffuseness measure

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2016-01-01

    This study presents a kurtosis analysis of room impulse responses as a potential room diffuseness measure. In the early part of an impulse response, sound pressure samples do not constitute a Gaussian distribution due to the direct sound and strong reflections. Such deterministic reflections...... are extreme events, which prevent the pressure samples from being normally distributed, leading to a high kurtosis. As the reflections are sparser and stronger, the sound field becomes less diffuse and the kurtosis systematically increases, indicating that it can be used as a diffuseness measure. The kurtosis...... converges to zero, as the reflection overlap becomes heavier, which is an important condition for a perfect diffuse field. Two rooms are analyzed. A small rectangular room shows that a non-uniform surface absorption distribution tends to increase the kurtosis significantly. A full scale reverberation...

  6. Solute Diffusivity in Undisturbed Soil

    DEFF Research Database (Denmark)

    Lægdsmand, Mette K.; Møldrup, Per; Schjønning, Per

    2012-01-01

    diffusivities independent of the tracer set used. We analyzed the whole data set using Archie's law and found a linear relation between Archie's exponent and the logarithm of the soil water matric suction in centimeters of water (pF). An analysis of seven data sets from the literature showed......Solute diffusivity in soil plays a major role in many important processes with relation to plant growth and environmental issues. Soil solute diffusivity is affected by the volumetric water content as well as the morphological characteristics of water-filled pores. The solute diffusivity in intact...... soil samples from two different tillage treatments (soil from below the depth of a harrow treatment and soil from within a moldboard plowed plow layer) was estimated based on concentration profiles using a newly developed method. The method makes use of multiple tracers (two sets of counterdiffusing...

  7. Diffusion of single oxidation pond

    Directory of Open Access Journals (Sweden)

    Song Ruo-Yuan

    2016-01-01

    Full Text Available The hydraulic characteristic of an oxidation pond was studied by the tracer experiment, and an empirical formula of Peclet number was obtained, which can be well applied to the model of plug flow reactor with longitudinal diffusion.

  8. Computational Diffusion MRI : MICCAI Workshop

    CERN Document Server

    Grussu, Francesco; Ning, Lipeng; Tax, Chantal; Veraart, Jelle

    2018-01-01

    This volume presents the latest developments in the highly active and rapidly growing field of diffusion MRI. The reader will find numerous contributions covering a broad range of topics, from the mathematical foundations of the diffusion process and signal generation, to new computational methods and estimation techniques for the in-vivo recovery of microstructural and connectivity features, as well as frontline applications in neuroscience research and clinical practice. These proceedings contain the papers presented at the 2017 MICCAI Workshop on Computational Diffusion MRI (CDMRI’17) held in Québec, Canada on September 10, 2017, sharing new perspectives on the most recent research challenges for those currently working in the field, but also offering a valuable starting point for anyone interested in learning computational techniques in diffusion MRI. This book includes rigorous mathematical derivations, a large number of rich, full-colour visualisations and clinically relevant results. As such, it wil...

  9. Geometric diffusion of quantum trajectories

    Science.gov (United States)

    Yang, Fan; Liu, Ren-Bao

    2015-07-01

    A quantum object can acquire a geometric phase (such as Berry phases and Aharonov-Bohm phases) when evolving along a path in a parameter space with non-trivial gauge structures. Inherent to quantum evolutions of wavepackets, quantum diffusion occurs along quantum trajectories. Here we show that quantum diffusion can also be geometric as characterized by the imaginary part of a geometric phase. The geometric quantum diffusion results from interference between different instantaneous eigenstate pathways which have different geometric phases during the adiabatic evolution. As a specific example, we study the quantum trajectories of optically excited electron-hole pairs in time-reversal symmetric insulators, driven by an elliptically polarized terahertz field. The imaginary geometric phase manifests itself as elliptical polarization in the terahertz sideband generation. The geometric quantum diffusion adds a new dimension to geometric phases and may have applications in many fields of physics, e.g., transport in topological insulators and novel electro-optical effects.

  10. Diffusivity in silicon 1953 to 2009

    CERN Document Server

    Fisher, David J

    2010-01-01

    This work is essentially an update of previous compilations of information on the diffusivity of elements in semiconductor-grade silicon. It subsumes the data contained in B.L.Sharma's monograph on 'Diffusion in Semiconductors' (Trans Tech Publications, 1970), plus the data contained in Diffusion and Defect Data (Diffusion in Silicon) Volume 45 (1986), Defect and Diffusion Forum (Diffusion in Silicon - 10 years of Research) Volumes 153-155 (1998), Defect and Diffusion Forum (Diffusion in Silicon - a Seven-Year Retrospective) Volume 241 (2005) and the latest data from recent Semiconductor Retro

  11. Boron diffusion in silicon devices

    Science.gov (United States)

    Rohatgi, Ajeet; Kim, Dong Seop; Nakayashiki, Kenta; Rounsaville, Brian

    2010-09-07

    Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.

  12. Diffusion through statically compacted clay

    International Nuclear Information System (INIS)

    Ho, C.L.; Shebl, M.A.A.

    1994-01-01

    This paper presents experimental work on the effect of compaction on contaminant flow through clay liners. The experimental program included evaluation of soil properties, compaction, permeability and solute diffusion. A permeameter was built of non reactive materials to test samples compacted at different water contents and compactive efforts. The flow of a permeating solute, LiCl, was monitored. Effluent samples were collected for solute concentration measurements. The concentrations were measured by performing atomic adsorption tests. The analyzed results showed different diffusion characteristics when compaction conditions changed. At each compactive effort, permeability decreased as molding water content increased. Consequently, transit time (measured at relative concentration 50%) increased and diffusivity decreased. As compactive effort increased for soils compacted dry of optimum, permeability and diffusion decreased. On the other hand, as compactive effort increased for soils compacted wet of optimum, permeability and diffusivity increased. Tortuosity factor was indirectly measured from the diffusion and retardation rate. Tortuosity factor also decreased as placement water content was increased from dry of optimum to wet of optimum. Then decreases were more pronounced for low compactive effort tests. 27 refs., 7 figs., 5 tabs

  13. Diffusion MRI findings in phenylketonuria

    Energy Technology Data Exchange (ETDEWEB)

    Sener, R.N. [Dept. of Radiology, Ege Univ. Hospital, Izmir (Turkey)

    2003-12-01

    Two patients with phenylketonuria were studied who were under dietary control since infancy, and who were mentally normal. Diffusion MRI was obtained using a spin-echo, echo-planar sequence with a gradient strength of 30 mT/m at 1.5 T. A trace sequence (TR=5700 ms, and TE=139 ms) was used, acquired in 22 s. Heavily diffusion-weighted (b=1000 mm{sup 2}/s) images, and the apparent diffusion coefficient (ADC) values from automatically generated ADC maps were studied. There were two different patterns in these two patients, restricted and increased diffusion patterns. Restricted diffusion pattern consisted of high-signal on b=1000 s/mm{sup 2} images with low ADC values ranging from 0.46 to 0.57 x 10{sup -3} mm{sup 2}/s. Increased diffusion pattern consisted of normal b=1000 s/mm{sup 2} images with high ADC values ranging from 1.37 to 1.63 x 10{sup -3} mm{sup 2}/s. It is likely that these values reflected presence of two different histopathological changes in phenylketonuria or reflected different stages of the same disease. (orig.)

  14. Diffusion MRI findings in phenylketonuria

    International Nuclear Information System (INIS)

    Sener, R.N.

    2003-01-01

    Two patients with phenylketonuria were studied who were under dietary control since infancy, and who were mentally normal. Diffusion MRI was obtained using a spin-echo, echo-planar sequence with a gradient strength of 30 mT/m at 1.5 T. A trace sequence (TR=5700 ms, and TE=139 ms) was used, acquired in 22 s. Heavily diffusion-weighted (b=1000 mm 2 /s) images, and the apparent diffusion coefficient (ADC) values from automatically generated ADC maps were studied. There were two different patterns in these two patients, restricted and increased diffusion patterns. Restricted diffusion pattern consisted of high-signal on b=1000 s/mm 2 images with low ADC values ranging from 0.46 to 0.57 x 10 -3 mm 2 /s. Increased diffusion pattern consisted of normal b=1000 s/mm 2 images with high ADC values ranging from 1.37 to 1.63 x 10 -3 mm 2 /s. It is likely that these values reflected presence of two different histopathological changes in phenylketonuria or reflected different stages of the same disease. (orig.)

  15. Diffusion processes in nuclear materials

    International Nuclear Information System (INIS)

    Agarwala, P.

    1992-01-01

    Diffusion phenomena have played an important role for the materials scientist in improving products in a variety of fields. An ever widening number of diffusion limited processes have found their way into development, fabrication and irradiation of nuclear materials in controlling grain growth, recrystallization, sintering, creep, etc. This volume gives a comprehensive overview on the various diffusion processes involved in nuclear materials, whether they are operative in fissionable or fissile nuclear fuels or in the prospective fuels or clads under passive or reactor operating conditions. Unless this information is well understood, it is not possible to develop or fabricate these fuels to withstand the vagaries of temperature, its gradient or changes in stoichiometry, role of defects and impurities in controlling diffusion processes in nuclear proper evaluation. On radiation, under reactor operating conditions, nuclear fuels undergo fission gas release resulting in precipitation into bubbles, or their venting, or radiation induced re-solution, the effects of this irradiation are also examined in depth. The work will be of value to all those interested in getting clearer insight into different mechanisms of diffusion, latest techniques of studying diffusion phenomena, effect of some the constraints such as impurities (chemical doping or fission product build up), and temperature and stoichiometry changes. (author). reds., figs., tabs

  16. Lead diffusion in monazite; Diffusion du plomb dans la monazite

    Energy Technology Data Exchange (ETDEWEB)

    Gardes, E

    2006-06-15

    Proper knowledge of the diffusion rates of lead in monazite is necessary to understand the U-Th-Pb age anomalies of this mineral, which is one of the most used in geochronology after zircon. Diffusion experiments were performed in NdPO{sub 4} monocrystals and in Nd{sub 0.66}Ca{sub 0.17}Th{sub 0.17}PO{sub 4} polycrystals from Nd{sub 0.66}Pb{sub 0.17}Th{sub 0.17}PO{sub 4} thin films to investigate Pb{sup 2+} + Th{sup 4+} {r_reversible} 2 Nd{sup 3+} and Pb{sup 2+} {r_reversible} Ca{sup 2+} exchanges. Diffusion annealings were run between 1200 and 1500 Celsius degrees, at room pressure, for durations ranging from one hour to one month. The diffusion profiles were analysed using TEM (transmission electronic microscopy) and RBS (Rutherford backscattering spectroscopy). The diffusivities extracted for Pb{sup 2+} + Th{sup 4+} {r_reversible} 2 Nd{sup 3+} exchange follow an Arrhenius law with parameters E equals 509 {+-} 24 kJ mol{sup -1} and log(D{sub 0} (m{sup 2}s{sup -1})) equals -3.41 {+-} 0.77. Preliminary data for Pb{sup 2+} {r_reversible} Ca{sup 2+} exchange are in agreement with this result. The extrapolation of our data to crustal temperatures yields very slow diffusivities. For instance, the time necessary for a 50 {mu}m grain to lose all of its lead at 800 Celsius degrees is greater than the age of the Earth. From these results and other evidence from the literature, we conclude that most of the perturbations in U-Th-Pb ages of monazite cannot be attributed to lead diffusion, but rather to interactions with fluids. (author)

  17. Drug diffusion across skin with diffusivity spatially modulated

    Science.gov (United States)

    Montoya Arroyave, Isabel

    2014-05-01

    A diffusion and delivery model of a drug across the skin with diffusivity spatially modulated is formulated and solved analytically using computer algebra. The model is developed using one-dimensional diffusion equation with a diffusivity which is a function of position in the skin; with an initial condition which is describing that the drug is initially contained inside a therapeutic patch; with a boundary condition according to which the change in concentration in the patch is minimal, such that assumption of zero flux at the patch-skin interface is valid; and with other boundary condition according to which the microcirculation in the capillaries just below the dermis carries the drug molecules away from the site at a very fast rate, maintaining the inner concentration at 0. The model is solved analytically by the method of the Laplace transform, with Bromwich integral and residue theorem. The concentration profile of the drug in the skin is expressed as an infinite series of Bessel functions. The corresponding total amount of delivered drug is expressed as an infinite series of decreasing exponentials. Also, the corresponding effective time for the therapeutic patch is determined. All computations were performed using computer algebra software, specifically Maple. The analytical results obtained are important for understanding and improving currentapplications of therapeutic patches. For future research it is interesting to consider more general models of spatial modulation of the diffusivity and the possible application of other computer algebra software such as Mathematica and Maxima.

  18. Ion diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    Lehikoinen, J.

    1999-03-01

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K d , unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.)

  19. Anomalous diffusion and diffusion anomaly in confined Janus dumbbells.

    Science.gov (United States)

    B Krott, Leandro; Gavazzoni, Cristina; Bordin, José Rafael

    2016-12-28

    Self-assembly and dynamical properties of Janus nanoparticles have been studied by molecular dynamic simulations. The nanoparticles are modeled as dimers and they are confined between two flat parallel plates to simulate a thin film. One monomer from the dumbbells interacts by a standard Lennard-Jones potential and the other by a two-length scales shoulder potential, typically used for anomalous fluids. Here, we study the effects of removing the Brownian effects, typical from colloidal systems immersed in aqueous solution, and consider a molecular system, without the drag force and the random collisions from the Brownian motion. Self-assembly and diffusion anomaly are preserved in relation to the Brownian system. Additionally, a superdiffusive regime associated to a collective reorientation in a highly structured phase is observed. Diffusion anomaly and anomalous diffusion are explained in the two length scale framework.

  20. Anomalous diffusion and diffusion anomaly in confined Janus dumbbells

    Science.gov (United States)

    Krott, Leandro B.; Gavazzoni, Cristina; Bordin, José Rafael

    2016-12-01

    Self-assembly and dynamical properties of Janus nanoparticles have been studied by molecular dynamic simulations. The nanoparticles are modeled as dimers and they are confined between two flat parallel plates to simulate a thin film. One monomer from the dumbbells interacts by a standard Lennard-Jones potential and the other by a two-length scales shoulder potential, typically used for anomalous fluids. Here, we study the effects of removing the Brownian effects, typical from colloidal systems immersed in aqueous solution, and consider a molecular system, without the drag force and the random collisions from the Brownian motion. Self-assembly and diffusion anomaly are preserved in relation to the Brownian system. Additionally, a superdiffusive regime associated to a collective reorientation in a highly structured phase is observed. Diffusion anomaly and anomalous diffusion are explained in the two length scale framework.

  1. Diffuse and vascular hepatic diseases; Diffuse und vaskulaere Lebererkrankungen

    Energy Technology Data Exchange (ETDEWEB)

    Kreimeyer, S.; Grenacher, L. [Universitaetsklinikum Heidelberg, Abteilung Diagnostische und Interventionelle Radiologie, Heidelberg (Germany)

    2011-08-15

    In addition to focal liver lesions, diffuse and vascular disorders of the liver represent a wide spectrum of liver diseases which are from the radiological point of view often difficult or nearly impossible to diagnose. Classical diagnostic methods are computed tomography and magnetic resonance imaging in addition to ultrasound. Diffuse parenchymal damage caused by diseases of various etiologies is therefore difficult to evaluate because it often lacks characteristic morphological features. For hepatic steatosis, hemochromatosis/siderosis as an example of a diffuse storage disease and sarcoidosis and candidiasis as infectious/inflammatory diseases, an image-based diagnosis is appropriate in some cases. For most diffuse liver diseases, however only nonspecific changes are visualized. Vascular pathologies of the liver, such as the Budd-Chiari syndrome and portal vein thrombosis, however, can usually be diagnosed very clearly using radiology and there is also a very effective interventional radiological treatment. Chronic diseases very often culminate in liver cirrhosis which is highly associated with an increased risk of liver cancer. (orig.) [German] Neben den fokalen Leberlaesionen stellen diffuse und vaskulaere Lebererkrankungen ein weites Spektrum an Erkrankungen der Leber dar, die radiologisch oft schwer oder gar nicht diagnostizierbar sind. Klassische diagnostische Verfahren sind dabei neben dem Ultraschall die Computertomographie und die Magnetresonanztomographie. Diffuse Parenchymschaeden, bedingt durch Erkrankungen unterschiedlichster Aetiologie, sind deshalb schwierig evaluierbar, weil haeufig charakteristische bildmorphologische Merkmale fehlen. Die Steatosis hepatis, die Haemochromatose/Siderose als Beispiel der Speicherkrankheiten sowie die Sarkoidose und die Candidose als infektioes-entzuendliche Erkrankungen sind einer bildbasierten Diagnosestellung z. T. zugaenglich, bei den meisten diffusen Lebererkrankungen jedoch zeigen sich lediglich unspezifische

  2. Radionuclide diffusion in soils. III

    International Nuclear Information System (INIS)

    Cipakova, A.; Szabova, T.

    1988-01-01

    Samples were taken of five soil types for determining diffusion coefficients, namely chernozem, illimerized brown soil, degraded chernozem, gleizated brown soil and heavy loamy brown soil. 5 layers of soil having a thickness of 1 cm each were placed in diffusion columns. 20 ml of water with 0.45 MBq 85 Sr of distilled water was poured over the columns. 10 ml of distilled water was poured over the columns every 5 days for monitoring the effect of the amount of precipitation and its distribution - a similarity with rainfall in the driest month, 41 ml of distilled water was then poured over the column every 5 days or 82 ml of distilled water every 10 days - imitating the month with the highest rainfall level. The effect of salts and various concentrations of salt mixtures on the value of the diffusion coefficient were monitored in solutions of NaNO 3 , KNO 3 and Ca(NO 3 ) 2 with added activity 0.45 MGq of 85 SrCl 2 . Diffusion was monitored for 101 days. All measured values are tabulated. The smallest diffusion coefficient was found in chernozem in the presence of H 2 O and the highest value was found in illimerized brown soil in the presence of 0.15 M of KNO 3 . (E.S.). 2 tabs., 10 refs

  3. Gaseous diffusion -- the enrichment workhorse

    International Nuclear Information System (INIS)

    Shoemaker, J.E. Jr.

    1984-01-01

    Construction of the first large-scale gaseous diffusion facility was started as part of the Manhattan Project in Oak Ridge, Tennessee, in 1943. This facility, code named ''K-25,'' began operation in January 1945 and was fully on stream by September 1945. Four additional process buildings were later added in Oak Ridge as the demand for enriched uranium escalated. New gaseous diffusion plants were constructed at Paducah, Kentucky, and Portsmouth, Ohio, during this period. The three gaseous diffusion plants were the ''workhorses'' which provided the entire enriched uranium demand for the United States during the 1950s and 1960s. As the demand for enriched uranium for military purposes decreased during the early 1960s, power to the diffusion plants was curtailed to reduce production. During the 1960s, as plans for the nuclear power industry were formulated, the role of the diffusion plants gradually changed from providing highly-enriched uranium for the military to providing low-enriched uranium for power reactors

  4. Diffusion of student business incubators

    DEFF Research Database (Denmark)

    Hjortsø, Carsten Nico Portefée; Honig, Benson; Riis, Nina Louise Fynbo

    This paper undertakes a longitudinal examination of the diffusion of a relatively new organizational activity - university student business incubators - by studying the processes through which actors grounded in three different institutional logics interact in the organizational field of higher....... The process was facilitated by the institutional logic of entrepreneurial culture that integrated elements of the commercial and classic university logics. We find that the diffusion and adaptation process were mainly influenced by resources available, organizational constituencies mobilized, discretional...... education. Applying neo-institutional theory, we examine the development of student incubation activities in the field of general state-funded Danish universities. We review institutional pressures from the political sphere that led to the diffusion of student incubation, introducing a three-phase process...

  5. Nonlinear Diffusion and Transient Osmosis

    International Nuclear Information System (INIS)

    Igarashi, Akira; Rondoni, Lamberto; Botrugno, Antonio; Pizzi, Marco

    2011-01-01

    We investigate both analytically and numerically the concentration dynamics of a solution in two containers connected by a narrow and short channel, in which diffusion obeys a porous medium equation. We also consider the variation of the pressure in the containers due to the flow of matter in the channel. In particular, we identify a phenomenon, which depends on the transport of matter across nano-porous membranes, which we call ''transient osmosis . We find that nonlinear diffusion of the porous medium equation type allows numerous different osmotic-like phenomena, which are not present in the case of ordinary Fickian diffusion. Experimental results suggest one possible candidate for transiently osmotic processes. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  6. Single Crystal Diffuse Neutron Scattering

    Directory of Open Access Journals (Sweden)

    Richard Welberry

    2018-01-01

    Full Text Available Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. In this paper, we compare three different instruments that have been used by us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.

  7. Innovation Diffusion: Assessment of Strategies within the Diffusion Simulation Game

    Science.gov (United States)

    Enfield, Jacob; Myers, Rodney D.; Lara, Miguel; Frick, Theodore W.

    2012-01-01

    Educators increasingly view the high level of engagement and experiential learning offered by games as a means to promote learning. However, as with any designed learning experience, player experiences should provide an accurate representation of content to be learned. In this study, the authors investigated the DIFFUSION SIMULATION GAME (DSG) to…

  8. Langevin diffusions on the torus

    DEFF Research Database (Denmark)

    García-Portugués, Eduardo; Sørensen, Michael; Mardia, Kanti V.

    2018-01-01

    We introduce stochastic models for continuous-time evolution of angles and develop their estimation. We focus on studying Langevin diffusions with stationary distributions equal to well-known distributions from directional statistics, since such diffusions can be regarded as toroidal analogues......) a likelihood based on the stationary distribution; (ii) toroidal adaptations of the Euler and Shoji–Ozaki pseudo-likelihoods; (iii) a likelihood based on a specific approximation to the transition density of the wrapped normal process. A simulation study compares, in dimensions one and two, the approximate...

  9. Oxygen diffusion in cuprate superconductors

    International Nuclear Information System (INIS)

    Routbort, J.L.; Rothman, S.J.

    1995-01-01

    Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La 2-x Sr x CuO 4 , YBa 2 Cu 3 O 7- δ, YBa 2 Cu 4 O 8 , and the Bi 2 Sr 2 Ca n-1 Cu n O 2+4 (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible

  10. Some Aspects of Diffusion Theory

    CERN Document Server

    Pignedoli, A

    2011-01-01

    This title includes: V.C.A. Ferraro: Diffusion of ions in a plasma with applications to the ionosphere; P.C. Kendall: On the diffusion in the atmosphere and ionosphere; F. Henin: Kinetic equations and Brownian motion; T. Kahan: Theorie des reacteurs nucleaires: methodes de resolution perturbationnelles, interactives et variationnelles; C. Cattaneo: Sulla conduzione del calore; C. Agostinelli: Formule di Green per la diffusione del campo magnetico in un fluido elettricamente conduttore; A. Pignedoli: Transformational methods applied to some one-dimensional problems concerning the equations of t

  11. Spatial Mapping of Translational Diffusion Coefficients Using Diffusion Tensor Imaging: A Mathematical Description.

    Science.gov (United States)

    Shetty, Anil N; Chiang, Sharon; Maletic-Savatic, Mirjana; Kasprian, Gregor; Vannucci, Marina; Lee, Wesley

    2014-01-01

    In this article, we discuss the theoretical background for diffusion weighted imaging and diffusion tensor imaging. Molecular diffusion is a random process involving thermal Brownian motion. In biological tissues, the underlying microstructures restrict the diffusion of water molecules, making diffusion directionally dependent. Water diffusion in tissue is mathematically characterized by the diffusion tensor, the elements of which contain information about the magnitude and direction of diffusion and is a function of the coordinate system. Thus, it is possible to generate contrast in tissue based primarily on diffusion effects. Expressing diffusion in terms of the measured diffusion coefficient (eigenvalue) in any one direction can lead to errors. Nowhere is this more evident than in white matter, due to the preferential orientation of myelin fibers. The directional dependency is removed by diagonalization of the diffusion tensor, which then yields a set of three eigenvalues and eigenvectors, representing the magnitude and direction of the three orthogonal axes of the diffusion ellipsoid, respectively. For example, the eigenvalue corresponding to the eigenvector along the long axis of the fiber corresponds qualitatively to diffusion with least restriction. Determination of the principal values of the diffusion tensor and various anisotropic indices provides structural information. We review the use of diffusion measurements using the modified Stejskal-Tanner diffusion equation. The anisotropy is analyzed by decomposing the diffusion tensor based on symmetrical properties describing the geometry of diffusion tensor. We further describe diffusion tensor properties in visualizing fiber tract organization of the human brain.

  12. Diffuse and vascular hepatic diseases

    International Nuclear Information System (INIS)

    Kreimeyer, S.; Grenacher, L.

    2011-01-01

    In addition to focal liver lesions, diffuse and vascular disorders of the liver represent a wide spectrum of liver diseases which are from the radiological point of view often difficult or nearly impossible to diagnose. Classical diagnostic methods are computed tomography and magnetic resonance imaging in addition to ultrasound. Diffuse parenchymal damage caused by diseases of various etiologies is therefore difficult to evaluate because it often lacks characteristic morphological features. For hepatic steatosis, hemochromatosis/siderosis as an example of a diffuse storage disease and sarcoidosis and candidiasis as infectious/inflammatory diseases, an image-based diagnosis is appropriate in some cases. For most diffuse liver diseases, however only nonspecific changes are visualized. Vascular pathologies of the liver, such as the Budd-Chiari syndrome and portal vein thrombosis, however, can usually be diagnosed very clearly using radiology and there is also a very effective interventional radiological treatment. Chronic diseases very often culminate in liver cirrhosis which is highly associated with an increased risk of liver cancer. (orig.) [de

  13. Intracellular transport by active diffusion

    NARCIS (Netherlands)

    Brangwynne, C. P.; Koenderink, G.H.; Mac Kintosh, F.C.; Weitz, D. A.

    2009-01-01

    All substances exhibit constant random motion at the microscopic scale. This is a direct consequence of thermal agitation, and leads to diffusion of molecules and small particles in a liquid. In addition to this nondirected motion, living cells also use active transport mechanisms, such as motor

  14. Diffusion of hydrogen in yttrium

    International Nuclear Information System (INIS)

    Vorobyov, V.V.; Ryabchikov, L.N.

    1966-01-01

    In this work the diffusion coefficients of hydrogen in yttrium were determined from the rate at which the hydrogen was released from yttrium samples under a vacuum at temperatures of 450 to 850 0 C and from the quantity of hydrogen retained by yttrium at hydrogen pressures below 5 x 10 - 4 mm Hg in the same temperature range

  15. Rotational diffusion in dense suspensions

    NARCIS (Netherlands)

    Hagen, M. H. J.; Frenkel, D.; Lowe, C.P.

    1999-01-01

    We have computed the rotational diffusion coefficient for a suspension of hard spheres. We find excellent agreement with experimental results over a density range up to, and including, the colloidal crystal. However, we find that theories derived to second order in the volume fraction overestimate

  16. Less Confusion in Diffusion MRI

    NARCIS (Netherlands)

    Tax, CMW

    2016-01-01

    With its unique ability to investigate tissue architecture and microstructure in vivo, diffusion MRI (dMRI) has gained tremendous interest and the society has been continuously triggered to develop novel dMRI image analysis approaches. With the overwhelming amount of strategies currently available

  17. Essays on diffusion and categories

    NARCIS (Netherlands)

    van Hugten, Joeri

    2015-01-01

    Essay’ derives from the French ‘to try’. Accordingly, in this book, I try three new interpretations of diffusion and categories. That is, I try to divide observations into groups in a new way. Some ways of dividing lead to confusion and frustration. For example, people’s default division seems to be

  18. Diffuse Infiltrative Lymphocytosis Syndrome (DILS)

    African Journals Online (AJOL)

    Abstract. Diffuse infiltrative lymphocytosis syndrome (DILS) is characterised by a persistent CD8+ lymphocytosis and lymphocytic infiltration of various organs. The reported prevalence varies between 0.85 – 3%, and appears to be more common in Africans. Patients with. DILS tend to have higher CD4+ cell counts and ...

  19. Unexpected consequences of bedload diffusion

    Science.gov (United States)

    Devauchelle, O.; Abramian, A.; Lajeunesse, E.

    2017-12-01

    Sedimentary grains transported as bedload bump and bounce on the rough bed of the river that entrains them. The succession of these random events causes bedload particles to diffuse across the flow, towards the less active areas of the bed. In a fashion reminiscent of that proposed by Parker (1978) for suspended load, this mechanism opposes gravity to maintain the banks of alluvial rivers. In fact, diffusion is so tightly linked to bedload that it appears in the most basic sediment transport experiment--the straight channel we use to calibrate transport laws. Indeed, the fixed sides of the channel cause the flow, and thus the bed shear stress, to vary across the flume. This variation induces bedload diffusion, which in turn deforms the bed. As a consequence, to reliably calibrate a transport law, we need to measure the full profiles of shear stress and bedload transport, rather than bulk-average these quantities. Unfortunately, using a larger channel does not solve the problem, as a large aspect ratio favors the growth of streaks caused by a diffusion-induced instability. Based on these observations, we propose a different design for sediment transport experiments.

  20. Uranium enrichment by diffusion process

    International Nuclear Information System (INIS)

    Petit, J.F.

    1977-01-01

    A brief history of the process is given, and existing facilities are described, and the possibility of this process meeting the needs for enriched uranium in the future is discussed. It is concluded that, since other separation techniques have not yet been proven to be competitive, the gaseous diffusion process must be relied on to meet most of these needs. However, because of the high energy consumption required by this process, attempts to improve the technology must be continued. Is the gaseous diffusion process able to meet this challenge. Considering the technical viewpoint, there is no doubt about it. From the economical standpoint, this process is mainly characterized by an important energy consumption and the necessity to build large plants, thus leading to an important investment, at least for the first plant. Other processes have been developed with a view to reduce both the energy and capital needs. However, in spite of continuous studies and technological progress no process has yet been proven to be competitive. Large increments in capacities are still expected to come from the gaseous diffusion and several projects taking into acount the improvements in the flexibility, automatization, reliability and a reduced investment, will be analysed. Coupling of new facilities to existing plants has already proven to be of great interest. This situation explains why further investigations concerning the gaseous diffusion are being carried on, together with the study of new processes [fr

  1. Anomalous diffusion without scale invariance

    Energy Technology Data Exchange (ETDEWEB)

    Hanyga, A [Department of Earth Sciences, University of Bergen, Allegaten 41, N5007 Bergen (Norway)

    2007-05-25

    Asymptotic behaviour of a new class of anomalous diffusion equations for subdiffusive transport defined in terms of generalized distributed fractional-order time derivatives is considered. The effect of slowly varying factors on the scaling function of asymptotic solutions is demonstrated. The origin of slowly varying scaling factors in the CTRW models is discussed.

  2. Absorbing-and-diffusing coating

    OpenAIRE

    Tkalich, N. V.; Mokeev, Yu. G.; Onipko, A. F.; Vashchenko, V. F.; Topchev, M. D.; Glebov, V. V.; Ivanchenko, Dmitrij D.; Kolchigin, Nikolay N.; Yevdokimov, V. V.

    2003-01-01

    The paper presents the results of complex experimental research of the absorbing-and-diffusing material "Contrast". It is shown to be an efficient wideband-camouflage material in the radiolocation and the video bands. Ways for improving the material characteristics are outlined.

  3. In vivo facilitated diffusion model.

    Directory of Open Access Journals (Sweden)

    Maximilian Bauer

    Full Text Available Under dilute in vitro conditions transcription factors rapidly locate their target sequence on DNA by using the facilitated diffusion mechanism. However, whether this strategy of alternating between three-dimensional bulk diffusion and one-dimensional sliding along the DNA contour is still beneficial in the crowded interior of cells is highly disputed. Here we use a simple model for the bacterial genome inside the cell and present a semi-analytical model for the in vivo target search of transcription factors within the facilitated diffusion framework. Without having to resort to extensive simulations we determine the mean search time of a lac repressor in a living E. coli cell by including parameters deduced from experimental measurements. The results agree very well with experimental findings, and thus the facilitated diffusion picture emerges as a quantitative approach to gene regulation in living bacteria cells. Furthermore we see that the search time is not very sensitive to the parameters characterizing the DNA configuration and that the cell seems to operate very close to optimal conditions for target localization. Local searches as implied by the colocalization mechanism are only found to mildly accelerate the mean search time within our model.

  4. Diffusion data in granite. Recommended values

    International Nuclear Information System (INIS)

    Ohlsson, Yvonne; Neretniks, I.

    1997-10-01

    Diffusion data for radionuclide transport in the porous matrix of rock are proposed for Swedish rock and ground waters, for performance assessment. Suggested data are based on an experimental diffusion study, where tritiated water was used as noninteracting diffusing species in stationary diffusion experiments in Aespoe fine grained granite and diorite. These data, for tritiated water, were used as reference in our study. For other species the effective diffusivities could be predicted from knowledge of the relative behaviour of these species to that of tritiated water. The behaviour is influenced by the difference in free water diffusivity and sometimes the existence of anion exclusion of surface diffusion. Apparent diffusivities are also calculated using sorption data, in addition to the effective diffusivities. Data are proposed for high saline and low saline ground water conditions

  5. Wright-Fisher diffusion bridges.

    Science.gov (United States)

    Griffiths, Robert C; Jenkins, Paul A; Spanò, Dario

    2017-10-06

    The trajectory of the frequency of an allele which begins at x at time 0 and is known to have frequency z at time T can be modelled by the bridge process of the Wright-Fisher diffusion. Bridges when x=z=0 are particularly interesting because they model the trajectory of the frequency of an allele which appears at a time, then is lost by random drift or mutation after a time T. The coalescent genealogy back in time of a population in a neutral Wright-Fisher diffusion process is well understood. In this paper we obtain a new interpretation of the coalescent genealogy of the population in a bridge from a time t∈(0,T). In a bridge with allele frequencies of 0 at times 0 and T the coalescence structure is that the population coalesces in two directions from t to 0 and t to T such that there is just one lineage of the allele under consideration at times 0 and T. The genealogy in Wright-Fisher diffusion bridges with selection is more complex than in the neutral model, but still with the property of the population branching and coalescing in two directions from time t∈(0,T). The density of the frequency of an allele at time t is expressed in a way that shows coalescence in the two directions. A new algorithm for exact simulation of a neutral Wright-Fisher bridge is derived. This follows from knowing the density of the frequency in a bridge and exact simulation from the Wright-Fisher diffusion. The genealogy of the neutral Wright-Fisher bridge is also modelled by branching Pólya urns, extending a representation in a Wright-Fisher diffusion. This is a new very interesting representation that relates Wright-Fisher bridges to classical urn models in a Bayesian setting. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Turbulent diffusion of small particles

    Energy Technology Data Exchange (ETDEWEB)

    Margolin, L.G.

    1977-11-01

    The diffusion of small, spherical, rigid particles suspended in an incompressible turbulent fluid, but not interacting with each other, was studied. As a stochastic process, the turbulent fluid velocity field is assumed to be homogeneous, isotropic and stationary. Assuming the Stokes regime, a particle of equation of motion is used which includes only the effects of Stokes drag and a virtual mass force and an exact solution is found for the particle velocity correlation function, for all times and initial conditions, in terms of a fluid velocity correlation function measured along the motion of the particle. This shows that for times larger than a certain time scale, the particle velocity correlation becomes stationary. The effect of small shears in the fluid velocity was considered, under the additional restrictions of a certain high frequency regime for the turbulence. The shears convected past the particle much faster than the growth of the boundary layer. New force terms due to the presence of such shears are calculated and incorporated into the equation of motion. A perturbation solution to this equation is constructed, and the resultant particle velocity correlation function and diffusion coefficient are calculated. To lowest order, the particle diffusivity is found to be unaltered by the presence of small mean flow shears. The last model treated is one in which particles traverse a turbulent fluid with a large mean velocity. Among other restrictions, linearized form drag is assumed. The diffusion coefficient for such particles was calculated, and found to be much smaller than the passive scalar diffusion coefficient. This agrees within 5 percent with the experimental results of Snyder and Lumley.

  7. Turbulent diffusion of small particles

    International Nuclear Information System (INIS)

    Margolin, L.G.

    1977-11-01

    The diffusion of small, spherical, rigid particles suspended in an incompressible turbulent fluid, but not interacting with each other, was studied. As a stochastic process, the turbulent fluid velocity field is assumed to be homogeneous, isotropic and stationary. Assuming the Stokes regime, a particle of equation of motion is used which includes only the effects of Stokes drag and a virtual mass force and an exact solution is found for the particle velocity correlation function, for all times and initial conditions, in terms of a fluid velocity correlation function measured along the motion of the particle. This shows that for times larger than a certain time scale, the particle velocity correlation becomes stationary. The effect of small shears in the fluid velocity was considered, under the additional restrictions of a certain high frequency regime for the turbulence. The shears convected past the particle much faster than the growth of the boundary layer. New force terms due to the presence of such shears are calculated and incorporated into the equation of motion. A perturbation solution to this equation is constructed, and the resultant particle velocity correlation function and diffusion coefficient are calculated. To lowest order, the particle diffusivity is found to be unaltered by the presence of small mean flow shears. The last model treated is one in which particles traverse a turbulent fluid with a large mean velocity. Among other restrictions, linearized form drag is assumed. The diffusion coefficient for such particles was calculated, and found to be much smaller than the passive scalar diffusion coefficient. This agrees within 5 percent with the experimental results of Snyder and Lumley

  8. Early restenose in a polymer-free Biolimus A9-coated stent (BioFreedom): A case report based on optical coherence tomography

    Energy Technology Data Exchange (ETDEWEB)

    Ellert, Julia, E-mail: jellert55@gmail.com; Antonsen, Lisbeth; Jensen, Lisette Okkels

    2017-04-15

    An 81-year-old male patient with a severe de novo coronary artery stenosis in the proximal left anterior descending artery was treated with a BioFreedom stent (3.5 × 11 mm), three months later, the patient was re-admitted with chest pain and slightly increased troponin. The angiogram showed a significant in-stent restenosis in the recently treated lesion. Optical coherence tomography revealed a fully expanded stent without areas of incomplete stent apposition. Severe immature neointimal hyperplasia without formation of thrombosis was visualized, causing a severe in-stent restenosis. An underlying plaque rupture within the mid-proximal part of the in-stent restenosis was evident. - Highlights: • OCT images revealed an expanded stent without areas of incomplete stent apposition. • Severe immature neointimal hyperplasia caused a severe in-stent restenosis. • No formation of thrombosis was visualized. • A plaque rupture within the mid-proximal part of the in-stent restenosis was evident.

  9. Diffraction and diffusion in room acoustics

    DEFF Research Database (Denmark)

    Rindel, Jens Holger; Rasmussen, Birgit

    1996-01-01

    Diffraction and diffusion are two phenomena that are both related to the wave nature of sound. Diffraction due to the finite size of reflecting surfaces and the design of single reflectors and reflector arrays are discussed. Diffusion is the result of scattering of sound reflected from surfaces...... that are not plane but curved or irregular. The importance of diffusion has been demonstrated in concert halls. Methods for the design of diffusing surfaces and the development of new types of diffusers are reviewed. Finally, the importance of diffraction and diffusion in room acoustic computer models is discussed....

  10. Bayesian regularization of diffusion tensor images

    DEFF Research Database (Denmark)

    Frandsen, Jesper; Hobolth, Asger; Østergaard, Leif

    2007-01-01

    Diffusion tensor imaging (DTI) is a powerful tool in the study of the course of nerve fibre bundles in the human brain. Using DTI, the local fibre orientation in each image voxel can be described by a diffusion tensor which is constructed from local measurements of diffusion coefficients along...... several directions. The measured diffusion coefficients and thereby the diffusion tensors are subject to noise, leading to possibly flawed representations of the three dimensional fibre bundles. In this paper we develop a Bayesian procedure for regularizing the diffusion tensor field, fully utilizing...

  11. In vivo P-31 MR diffusion spectroscopy

    International Nuclear Information System (INIS)

    Moonen, C.T.W.; Vanzijl, P.C.M.; LeBihan, D.

    1988-01-01

    This paper discusses the Stejskal-Tanner diffusion spin-echo sequence modified for the in vivo diffusion spectroscopy. The apparent diffusion constant D α was measured as a function of the diffusion time. Contrary to the results in phantom samples, a strong dependency of the D α for phosphocreatine (PCr) in the rat muscle tissue on diffusion time was observed, clearly indicating restricted diffusion effects and allowing an approximation of the size of the restricted volume (8-13 μm). This size fits well with the known dimensions of a normal muscle cell

  12. Oceanic diffusion in the coastal area

    International Nuclear Information System (INIS)

    Rukuda, Masaaki

    1980-03-01

    Described in this paper is the eddy diffusion in the area off Tokai Village investigated by means of dye diffusion experiment and of oceanic observation. In order to assess the oceanic diffusion in coastal areas, improved methods effective in complex field were developed. The oceanic diffusion was separated in two groups, horizontal and vertical diffusion respectively. Both these diffusions are combined and their analysis together is difficult. The oceanic diffusion is thus considered separately. Instantaneous point release is the basis of horizontal diffusion analysis. Continuous release is then the overlap of numerous instantaneous releases. It was shown that the diffusion parameters derived from the results of diffusion experiment or oceanic observation vary widely with time and place and with sea conditions. A simple diffusion equation was developed from the equation of continuity. The results were in good agreement with seasonal mean horizontal distribution of river water in the sea area. The vertical observation in diffusion experiment is difficult and the vertical structure of oceanic condition is complex, so that the research on vertical diffusion generally is not advanced yet. With river water as the tracer, a method of estimating vertical diffusion parameters with a Gaussian model or one-dimensional model was developed. The vertical diffusion near sea bottom was numerically analized with suspended particles in seawater as the tracer. Diffusion was computed for each particle size, and by summing up the vertical distribution of beam attenuation coefficient was estimated. By comparing the results of estimation and those of observation the vertical diffusivity and the particle size distribution at sea bottom could be estimated. (author)

  13. Analytical boron diffusivity model in silicon for thermal diffusion from boron silicate glass film

    Science.gov (United States)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2015-09-01

    An analytical boron diffusivity model in silicon for thermal diffusion from a boron silicate glass (BSG) film has been proposed in terms of enhanced diffusion due to boron-silicon interstitial pair formation. The silicon interstitial generation is considered to be a result of the silicon kick-out mechanism by the diffused boron at the surface. The additional silicon interstitial generation in the bulk silicon is considered to be the dissociation of the diffused pairs. The former one causes the surface boron concentration dependent diffusion. The latter one causes the local boron concentration dependent diffusion. The calculated boron profiles based on the diffusivity model are confirmed to agree with the actual diffusion profiles measured by secondary ion mass spectroscopy (SIMS) for a wide range of the BSG boron concentration. This analytical diffusivity model is a helpful tool for p+ boron diffusion process optimization of n-type solar cell manufacturing.

  14. Theory and experiments on surface diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Silvestri, W.L.

    1998-11-01

    The following topics were dealt with: adatom formation and self-diffusion on the Ni(100) surface, helium atom scattering measurements, surface-diffusion parameter measurements, embedded atom method calculations.

  15. Diffus lungesygdom hos børn

    DEFF Research Database (Denmark)

    Buchvald, Frederik; Nielsen, Kim G

    2014-01-01

    Diffuse lung disease in children represents a heterogeneous group of respiratory disorders with high morbidity and mortality. Typical features include tachypnoea, failure to thrive, diffuse radiological and histopathological abnormalities. Advances in genetics and pathophysiology, combined...

  16. Devil's in the (diffuse) detail

    International Nuclear Information System (INIS)

    Welberry, R.

    2006-07-01

    X-ray crystallography is an important workhorse in the world of solid-state chemistry. However, while it's a powerful tool in determining the average structure in a crystal lattice, conventional crystallography is very limited when it comes to understanding nano-scale disorder within that crystal structure. And when it comes to understanding the properties of many important materials, the devil is in the detail. X-ray diffraction is still one of the keys to understanding this finer scale structure but using it requires a capacity to read between the lines - to understand the diffuse diffraction that most crystallography ignores. Scientists at the Research School of Chemistry are leading the world in this field. Their work on modelling nano-scaled disorder using diffuse diffraction is opening up new possibilities in understanding and modifying many of our most important materials

  17. CT of diffuse pulmonary diseases

    International Nuclear Information System (INIS)

    Itoh, Harumi; Murata, Kiyoshi; Todo, Giro

    1987-01-01

    While the theory of chest radiographic interpretation in diagnosing diffuse pulmonary diseases has not yet been established, X-ray computed tomography (CT), having intrinsic high contrast resolution and improved spatial resolution, has proved to offer important imformation concerning the location and invasion of diffuse pulmonary lesions. This study related to CT-pathologic correlation, focusing on perivascular interstitial space and secondary pulmonary lobule at macroscopic levels. The perivascular interstitial space was thickened as a result of the infiltration of cancer, granulomas, and inflammatory cells. This finding appeared as irregular contour of the blood vessel on CT. Centrilobular nodules were distributed at the tip of the bronchus or pulmonary artery on CT. The distance from the terminal and respiratory bronchioles to the lobular border was 2 to 3 mm. Lobular lesions were delineated as clear margin on CT. Contribution of these CT features to chest radiographic interpretation must await further studies. (Namekawa, K.)

  18. Massively parallel diffuse optical tomography

    Energy Technology Data Exchange (ETDEWEB)

    Sandusky, John V.; Pitts, Todd A.

    2017-09-05

    Diffuse optical tomography systems and methods are described herein. In a general embodiment, the diffuse optical tomography system comprises a plurality of sensor heads, the plurality of sensor heads comprising respective optical emitter systems and respective sensor systems. A sensor head in the plurality of sensors heads is caused to act as an illuminator, such that its optical emitter system transmits a transillumination beam towards a portion of a sample. Other sensor heads in the plurality of sensor heads act as observers, detecting portions of the transillumination beam that radiate from the sample in the fields of view of the respective sensory systems of the other sensor heads. Thus, sensor heads in the plurality of sensors heads generate sensor data in parallel.

  19. Erbium diffusion in titanium dioxide

    Directory of Open Access Journals (Sweden)

    Louise Basse

    2017-04-01

    Full Text Available The diffusivity of erbium in the anatase phase of titanium dioxide (TiO2 has been studied for various temperatures ranging from 800 °C to 1, 000 °C. Samples of TiO2, with a 10 nm thick buried layer containing 0.5 at% erbium, were fabricated by radio-frequency magnetron sputtering and subsequently heat treated. The erbium concentration profiles were measured by secondary ion mass spectrometry, allowing for determination of the temperature-dependent diffusion coefficients. These were found to follow an Arrhenius law with an activation energy of ( 2.1 ± 0.2 eV. X-ray diffraction revealed that the TiO2 films consisted of polycrystalline grains of size ≈ 100 nm.

  20. Information filtering via preferential diffusion

    Science.gov (United States)

    Lü, Linyuan; Liu, Weiping

    2011-06-01

    Recommender systems have shown great potential in addressing the information overload problem, namely helping users in finding interesting and relevant objects within a huge information space. Some physical dynamics, including the heat conduction process and mass or energy diffusion on networks, have recently found applications in personalized recommendation. Most of the previous studies focus overwhelmingly on recommendation accuracy as the only important factor, while overlooking the significance of diversity and novelty that indeed provide the vitality of the system. In this paper, we propose a recommendation algorithm based on the preferential diffusion process on a user-object bipartite network. Numerical analyses on two benchmark data sets, MovieLens and Netflix, indicate that our method outperforms the state-of-the-art methods. Specifically, it can not only provide more accurate recommendations, but also generate more diverse and novel recommendations by accurately recommending unpopular objects.

  1. Chronic Diffuse Alopecia In Female

    Directory of Open Access Journals (Sweden)

    Roy Aloke K

    1997-01-01

    Full Text Available Fifty female patients, in the age range 3.5 to 45 yrs, suffering from chronic diffuse alopecia were studied for the probable causes. In 26% of cases, iron deficiency anaemia was found to be the major aetiological factor and 20% cases showed hupothyroidism. The cause could not be traced in 40% of cases. In majority of cases, multiple factors might be implicated.

  2. Positron diffusion in noble gases

    International Nuclear Information System (INIS)

    Stromswold, D.C.; Lee, Y.K.

    1975-01-01

    Positron diffusion in helium, neon, and argon has been observed and the lifetimes of free positrons in these gases have been calculated on the basis of assumed theoretical behavior. The results are summarized for various gas pressures at room temperature. Reported lifetimes are comparable to the extrapolated values of 1.4 μsec in He and 0.2 μsec in Ar obtained at one atmosphere by Falk. (7 figures, 2 tables) (U.S.)

  3. Composite interlayer for diffusion bonding

    International Nuclear Information System (INIS)

    1976-01-01

    A ductile interlayer is described, which is useful for transient liquid phase diffusion bonding of metallic articles; the interlayer consisting of a melting point depressant and a plurality of ductile lamellae which are free from carbides, aluminides and borides. The composition and fabrication of the lamellae, and the process for bonding the metallic articles, depend on the composition of the metals to be bonded, and are exemplified in the specification. (U.K.)

  4. Thermal conductivity and thermal diffusivity

    International Nuclear Information System (INIS)

    Hust, J.G.

    1983-01-01

    This chapter examines the heat transfer properties of solids, with emphasis on the behavior of pure metals and alloys. Topics considered include electronic conduction, magnetic field effects, lattice conduction, measuring methods, specimen size, uncertainty, thermal anchoring, radial heat loss, thermal conductivity apparatus, thermal diffusivity apparatus, empirical correlations, the Wiedemann-Franz-Lorenz law, Matthiessen's rule, low-temperature correlation, predictive techniques, crystalline dielectrics, and disordered dielectrics. The materials examined include copper, aluminium, binary alloys, structural alloys, and structural composites

  5. The generalized Airy diffusion equation

    Directory of Open Access Journals (Sweden)

    Frank M. Cholewinski

    2003-08-01

    Full Text Available Solutions of a generalized Airy diffusion equation and an associated nonlinear partial differential equation are obtained. Trigonometric type functions are derived for a third order generalized radial Euler type operator. An associated complex variable theory and generalized Cauchy-Euler equations are obtained. Further, it is shown that the Airy expansions can be mapped onto the Bessel Calculus of Bochner, Cholewinski and Haimo.

  6. Fractional diffusion in inhomogeneous media

    Energy Technology Data Exchange (ETDEWEB)

    Chechkin, A V [Institute for Theoretical Physics, National Science Center ' Kharkov Institute of Physics and Technology' , Akademicheskaya St. 1, Kharkov 61108 (Ukraine); Gorenflo, R [Department of Mathematics and Informatics, Free University of Berlin, Arnimallee 3, D-14195 Berlin, Dahlem (Germany); Sokolov, I M [Institute for Physics, Humboldt University of Berlin, Newtonstrasse 15, D-12489 Berlin (Germany)

    2005-10-21

    Starting from the continuous time random walk (CTRW) scheme with the space-dependent waiting-time probability density function (PDF) we obtain the time-fractional diffusion equation with varying in space fractional order of time derivative. As an example, we study the evolution of a composite system consisting of two separate regions with different subdiffusion exponents and demonstrate the effects of non-trivial drift and subdiffusion whose laws are changed in the course of time. (letter to the editor)

  7. Rapid Innovation Diffusion in Social Networks

    OpenAIRE

    H Peyton Young; Gabriel E. Kreindler

    2012-01-01

    The diffusion of an innovation can be represented by a process in which agents choose perturbed best responses to what their neighbors are currently doing. Diffusion is said to be fast if the expected waiting time until the innovation spreads widely is bounded above independently of the size of the network. Previous work has identified specific topological properties of networks that guarantee fast diffusion. Here we apply martingale theory to derive topology-free bounds such that diffusion i...

  8. Diffusion in ordered binary solid systems

    International Nuclear Information System (INIS)

    Stolwijk, N.A.

    1980-01-01

    This thesis contains contributions to the field of diffusion in ordered binary solid systems. An extensive experimental investigation of the self diffusion in CoGa is presented. The results of these diffusion measurements strongly suggest that a substantial part of the atomic migration is caused by a new type of defect. A quantitative description of the atomic displacements via this defect is given. Finally computer simulations are presented of diffusion and ordering in binary solid systems. (Auth.)

  9. Application of NAA in diffusion studies

    International Nuclear Information System (INIS)

    Rajurkar, N.S.; Jha, S.; Gokarn, N.A.

    2001-01-01

    The diffusion of Mn 2+ ions in CoSO 4 , NiSO 4 and ZnSO 4 containing 1% agar gel as well as that of MnSO 4 in 1% agar gel was studied at 25 deg C. The diffusion coefficients at selected concentrations were determined by the zone diffusion technique and by measuring the concentration of diffusing ions using neutron activation analysis. (author)

  10. Energetic funnel facilitates facilitated diffusion.

    Science.gov (United States)

    Cencini, Massimo; Pigolotti, Simone

    2018-01-25

    Transcription factors (TFs) are able to associate to their binding sites on DNA faster than the physical limit posed by diffusion. Such high association rates can be achieved by alternating between three-dimensional diffusion and one-dimensional sliding along the DNA chain, a mechanism-dubbed facilitated diffusion. By studying a collection of TF binding sites of Escherichia coli from the RegulonDB database and of Bacillus subtilis from DBTBS, we reveal a funnel in the binding energy landscape around the target sequences. We show that such a funnel is linked to the presence of gradients of AT in the base composition of the DNA region around the binding sites. An extensive computational study of the stochastic sliding process along the energetic landscapes obtained from the database shows that the funnel can significantly enhance the probability of TFs to find their target sequences when sliding in their proximity. We demonstrate that this enhancement leads to a speed-up of the association process. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  11. Diffusion of hydrogen (1); cyclohexanol (2)

    Science.gov (United States)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) hydrogen; (2) cyclohexanol

  12. Diffusion of argon (1); cyclohexanol (2)

    Science.gov (United States)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) argon; (2) cyclohexanol

  13. Diffusion of nitrogen (1); cyclohexanol (2)

    Science.gov (United States)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) nitrogen; (2) cyclohexanol

  14. Mathematical methods for diffusion MRI processing

    International Nuclear Information System (INIS)

    Lenglet, C.; Lenglet, C.; Sapiro, G.; Campbell, J.S.W.; Pike, G.B.; Campbell, J.S.W.; Siddiqi, K.; Descoteaux, M.; Haro, G.; Wassermann, D.; Deriche, R.; Wassermann, D.; Anwander, A.; Thompson, P.M.

    2009-01-01

    In this article, we review recent mathematical models and computational methods for the processing of diffusion Magnetic Resonance Images, including state-of-the-art reconstruction of diffusion models, cerebral white matter connectivity analysis, and segmentation techniques. We focus on Diffusion Tensor Images (DTI) and Q-Ball Images (QBI). (authors)

  15. Explosive instabilities of reaction-diffusion equations

    Science.gov (United States)

    Wilhelmsson, H.

    1987-07-01

    Explicit solutions are obtained for evolution equations for explosively unstable situations. These solutions include the effects of diffusion with linear or quadratic density dependence of the diffusion coefficient. As a result of balance between the diffusion and nonlinear terms, explosive growth in time can occur with a preservation in shape of certain spatial distributions. The solutions are generalized to cases of two interacting populations.

  16. U diffusion in Ti-α

    International Nuclear Information System (INIS)

    Gordillo, J.; Perez, R.A.; Di Lalla, N.

    2012-01-01

    The spectrometry was used to measure the diffusion of u in Ti-α in the range of temperatures from 863 to 1123 k (590-850 o C). The diffusion parameters found Q = 294 kj / mol and D o = 4x10 -3 m2 / s are similar to obtained for the self-diffusion in Ti-? measured using a base material containing impurities like this work. This is consistent with the hypothesis that u diffuses via a vacancy mechanism in the grid of Ti-α and it contrasted with older results, in which the activation energy is significantly lower and incompatible with said diffusion mechanism (author)

  17. Diffusion of cobalt in alpha zirconium

    International Nuclear Information System (INIS)

    Ghosh, U.; Pruthi, D.D.; Anand, M.S.

    1979-01-01

    The diffusion of 60 Co in alpha zirconium has been studied in the temperature range of 873-1123 K using the sectioning technique. The diffusion parameters obey the following Arrhenius equation:- D = (1.132 +- 0.22)10 -4 exp((-136.43 +- 3.50 KJ)/RT)m 2 s -1 . The diffusivity in this phase is as high as that observed in β-phase. It is also about five orders of magnitude higher when compared to the self diffusion values. The high diffusivity of cobalt in alpha zirconium has been explained on the basis of an interstitial mechanism. (auth.)

  18. Research of Innovation Diffusion on Industrial Networks

    Directory of Open Access Journals (Sweden)

    Yongtai Chen

    2014-01-01

    Full Text Available The real value of innovation consists in its diffusion on industrial network. The factors which affect the diffusion of innovation on industrial network are the topology of industrial network and rules of diffusion. Industrial network is a complex network which has scale-free and small-world characters; its structure has some affection on threshold, length of path, enterprise’s status, and information share of innovation diffusion. Based on the cost and attitude to risk of technical innovation, we present the “avalanche” diffusing model of technical innovation on industrial network.

  19. Evaluation of empirical atmospheric diffusion data

    Energy Technology Data Exchange (ETDEWEB)

    Horst, T.W.; Doran, J.C.; Nickola, P.W.

    1979-10-01

    A study has been made of atmospheric diffusion over level, homogeneous terrain of contaminants released from non-buoyant point sources up to 100 m in height. Current theories of diffusion are compared to empirical diffusion data, and specific dispersion estimation techniques are recommended which can be implemented with the on-site meteorological instrumentation required by the Nuclear Regulatory Commission. A comparison of both the recommended diffusion model and the NRC diffusion model with the empirical data demonstrates that the predictions of the recommended model have both smaller scatter and less bias, particularly for ground-level sources.

  20. Evaluation of empirical atmospheric diffusion data

    International Nuclear Information System (INIS)

    Horst, T.W.; Doran, J.C.; Nickola, P.W.

    1979-10-01

    A study has been made of atmospheric diffusion over level, homogeneous terrain of contaminants released from non-buoyant point sources up to 100 m in height. Current theories of diffusion are compared to empirical diffusion data, and specific dispersion estimation techniques are recommended which can be implemented with the on-site meteorological instrumentation required by the Nuclear Regulatory Commission. A comparison of both the recommended diffusion model and the NRC diffusion model with the empirical data demonstrates that the predictions of the recommended model have both smaller scatter and less bias, particularly for groundlevel sources

  1. Modeling Internet Diffusion in Developing Countries

    Directory of Open Access Journals (Sweden)

    Scott McCoy

    2012-04-01

    Full Text Available Despite the increasing importance of the Internet, there is little work that addresses the degree to which the models and theories of Internet diffusion in developed countries can be applied to Internet diffusion in developing countries. This paper presents the first attempt to address this issue through theory driven modeling of Internet diffusion. Consistent with previous research, our findings suggest that economic development and technology infrastructure are musts for Internet diffusion. Interestingly, users’ cognition and government policies can accelerate Internet diffusion only after a certain level of human rights has been reached in a developing country.

  2. Using light transmission to watch hydrogen diffuse.

    Science.gov (United States)

    Pálsson, Gunnar K; Bliersbach, Andreas; Wolff, Max; Zamani, Atieh; Hjörvarsson, Björgvin

    2012-06-12

    Because of its light weight and small size, hydrogen exhibits one of the fastest diffusion rates in solid materials, comparable to the diffusion rate of liquid water molecules at room temperature. The diffusion rate is determined by an intricate combination of quantum effects and dynamic interplay with the displacement of host atoms that is still only partially understood. Here we present direct observations of the spatial and temporal changes in the diffusion-induced concentration profiles in a vanadium single crystal and we show that the results represent the experimental counterpart of the full time and spatial solution of Fick's diffusion equation. We validate the approach by determining the diffusion rate of hydrogen in a single crystal vanadium (001) film, with net diffusion in the [110] direction.

  3. Ion diffusion through highly compacted bentonite

    International Nuclear Information System (INIS)

    Eriksen, T.; Jacobsson, A.; Pusch, R.

    1981-01-01

    Compacted Na- and Ca-bentonites were contacted with aqueous solutions of 134 Cs + , 85 Sr 2+ , 131 I - and 36 Cl - and the diffusivities calculated from tracer concentration-distance profiles in the bentonites 10 days after the onset of diffusion. In the case of 131 I - and 36 Cl - the diffusivities were also determined by measuring the steady state transport through a 5 mm thick bentonite disc. The experimental results indicate that the diffusion through compacted bentonite is governed by complex mechanisms and cannot be accomodated by a simple pore diffusion model. It seems reasonable to assume that non-sorbing ions migrate in the pore water, while cations also move through smectic crystal lattices, preferably through interlamellar spacings according to an ion-exchange-type model. The very low diffusion rate of the investigated anions, as compared with the corresponding rate in bulk water, verifies that the diffusive resistance is very strong for these ions. (Auth.)

  4. Aspects of diffusion in the stadium billiard

    Science.gov (United States)

    Lozej, Črt; Robnik, Marko

    2018-01-01

    We perform a detailed numerical study of diffusion in the ɛ stadium of Bunimovich, and propose an empirical model of the local and global diffusion for various values of ɛ with the following conclusions: (i) the diffusion is normal for all values of ɛ (≤0.3 ) and all initial conditions, (ii) the diffusion constant is a parabolic function of the momentum (i.e., we have inhomogeneous diffusion), (iii) the model describes the diffusion very well including the boundary effects, (iv) the approach to the asymptotic equilibrium steady state is exponential, (v) the so-called random model (Robnik et al., 1997) is confirmed to apply very well, (vi) the diffusion constant extracted from the distribution function in momentum space and the one derived from the second moment agree very well. The classical transport time, an important parameter in quantum chaos, is thus determined.

  5. Study of the uranium-zirconium diffusion

    International Nuclear Information System (INIS)

    Adda, Y.; Mairy, C.; Bouchet, P.

    1957-01-01

    The intermetallic diffusion of uranium fuel and zirconium used as cladding is studied. Intermetallic diffusion can occur during the cladding of uranium rods and uranium can penetrate the zirconium cladding. Different parameters are involved in this mechanism as structure and mechanical properties of the diffusion area as well as presence of impurities in the metal. The uses of different analysis techniques (micrography, Castaing electronic microprobe, microhardness and autoradiography) have permitted to determine with great accuracy the diffusion coefficient in gamma phase (body centered cubic system) and the results have given important information on the intermetallic diffusion mechanisms. The existence of the Kirkendall effect in the U-Zr diffusion is also an argument in favor of the generality of the diffusion mechanism by vacancies in body centered cubic system. (M.P.)

  6. Diffusion of Implanted Radioisotopes in Solids

    CERN Multimedia

    2002-01-01

    Implantation of radioisotopes into metal and semiconductor samples is performed. The implanted isotope or its decay-product should have a half-life long enough for radiotracer diffusion experiments. Such radioisotopes are utilized to investigate basic diffusion properties in semiconductors and metals and to improve our understanding of the atomic mechanisms of diffusion. For suitably chosen systems the combination of on-line production and clean implantation of radioisotopes at the ISOLDE facility opens new possibilities for diffusion studies in solids. \\\\ \\\\ The investigations are concentrated on diffusion studies of $^{195}$Au in amorphous materials. The isotope $^{195}$Au was obtained from the mass 195 of the mercury beam. $^{195}$Hg decays into $^{195}$Au which is a very convenient isotope for diffusion experiments. \\\\ \\\\ It was found that $^{195}$Au is a slow diffusor in amorphous Co-Zr alloys, whereas Co is a fast diffusor in the same matrix. The ``asymmetry'' in the diffusion behaviour is of considerab...

  7. Probing the diffuse interstellar medium with diffuse interstellar bands

    Science.gov (United States)

    Theodorus van Loon, Jacco; Bailey, Mandy; Farhang, Amin; Javadi, Atefeh; Khosroshahi, Habib

    2015-08-01

    For a century already, a large number of absorption bands have been known at optical wavelengths, called the diffuse interstellar bands (DIBs). While their carriers remain unidentified, the relative strengths of these bands in various environments make them interesting new probes of the diffuse interstellar medium (ISM). We present the results from two large, dedicated campaigns to map the ISM using DIBs measured in the high signal-to-noise spectra of hundreds of early-type stars: [1] in and around the Local Bubble using ESO's New Technology Telescope and the Isaac Newton Telescope, and [2] across both Magellanic Clouds using the Very Large Telescope and the Anglo-Australian Telescope. We discuss the implications for the structure and dynamics of the ISM, as well as the constraints these maps place on the nature of the carriers of the DIBs. Partial results have appeared in the recent literature (van Loon et al. 2013; Farhang et al. 2015a,b; Bailey, PhD thesis 2014) with the remainder being prepared for publication now.

  8. Diffusive separation of particles by diffusion in swirled turbulent flows

    International Nuclear Information System (INIS)

    Arbuzov, V.N.; Shiliaev, M.I.

    1984-01-01

    An analysis of the dynamics of turbulent flow and diffusive separation of solid particles in a centrifugal air separator (consisting of two flat disks rotating at the same angular velocity) is presented. A closed set of balances for all the components of the tensor of turbulent stresses, extended to the entire flow region, is employed in the numerical analysis of transition and turbulent air flows between the rotating disks. The analytical relationships obtained for the case of the mixed flow for the various components of the average velocity, energy of fluctuations, and turbulence level in the circumferential direction agreed well with the theoretical and experimental distributions of Bakke, et al. (1973). It is shown that at high Reynolds numbers the flow is isotropic, the dependence of the circumferential component of the average velocity obeys a power law, and the generation of the radial component is controlled by the local centrifugal field. The sharpness of particle separation was calculated by the eddy diffusion equation and was found to depend on the geometry and the operating conditions. 8 references

  9. Biomimicry, vascular restenosis and coronary stents.

    Science.gov (United States)

    Schwartz, R S; van der Giessen, W J; Holmes, D R

    1998-01-01

    Biomimicry is in its earliest stages and is being considered in the realm of tissue engineering. If arterial implants are to limit neointimal thickening, purely passive structures cannot succeed. Bioactivity must be present, either by pharmacologic intervention or by fabricating a 'living stent' that contains active cellular material. As tissue engineering evolves, useful solutions will emerge from applying this knowledge directly to vascular biologic problems resulting from angioplasty, stenting, and vascular prosthesis research.

  10. A Mixed Blessing : Radioactivity Against Restenosis

    NARCIS (Netherlands)

    Clarijs, M.; Van Eijk, C.; Van Den Berg, R.

    2001-01-01

    Since their discovery a little over a century ago, X-rays and radioactivity have been used in numerous applications, from medical care to the process industry.We have also become acutely aware of the damaging effects both can have on the human body. This is the reason for the never-ending research

  11. Endovascular photodynamic therapy to prevent arterial restenosis

    NARCIS (Netherlands)

    E.E.E. Gabeler

    2003-01-01

    markdownabstract__Abstract__ Since their existence, man has appreciated the benefits of sunlight and described some of its medicinal effects known as heliotherapy. Herodotus in the 6th century BC noticed that sunlight had beneficial effects on bone growth. Hippocrates in 460-375 BC advocated

  12. Dosimetry implant for treating restenosis and hyperplasia

    Science.gov (United States)

    Srivastava, Suresh; Gonzales, Gilbert R; Howell, Roger W; Bolch, Wesley E; Adzic, Radoslav

    2014-09-16

    The present invention discloses a method of selectively providing radiation dosimetry to a subject in need of such treatment. The radiation is applied by an implant comprising a body member and .sup.117mSn electroplated at selected locations of the body member, emitting conversion electrons absorbed immediately adjacent selected locations while not affecting surrounding tissue outside of the immediately adjacent area.

  13. Diffusion in Altered Tonalite Sample Using Time Domain Diffusion Simulations in Tomographic Images Combined with Lab-scale Diffusion Experiments

    Science.gov (United States)

    Voutilainen, M.; Sardini, P.; Togneri, L.; Siitari-Kauppi, M.; Timonen, J.

    2010-12-01

    In this work an effect of rock heterogeneity on diffusion was investigated. Time domain diffusion simulations were used to compare behavior of diffusion in homogeneous and heterogeneous 3D media. Tomographic images were used as heterogeneous rock media. One altered tonalite sample from Sievi, Finland, was chosen as test case for introduced analysis procedure. Effective diffusion coefficient of tonalite sample was determined with lab-scale experiments and the same coefficient was used also for homogeneous media. Somewhat technically complicated mathematical solution for analysis of through diffusion experiment is shortly described. Computed tomography (CT) is already quite widely used in many geological, petrological, and paleontological applications when the three-dimensional (3D) structure of the material is of interest, and is an excellent method for gaining information especially about its heterogeneity, grain size, or porosity. In addition to offering means for quantitative characterization, CT provides a lot of qualitative information [1]. A through -diffusion laboratory experiment using radioactive tracer was fitted using the Time Domain Diffusion (TDD) method. This rapid particle tracking method allows simulation of the heterogeneous diffusion based on pore-scale images and local values of diffusivities [2]. As a result we found out that heterogeneity has only a small effect to diffusion coefficient and in-diffusion profile for used geometry. Also direction dependency was tested and was found to be negligible. Whereas significant difference between generally accepted value and value obtained from simulations for constant m in Archie’s law was found. [1] Voutilainen, M., Siitari-Kauppi, M., Sardini, P., and Timonen, J., (2010). On pore-space characterization of an altered tonalite by X-ray µCT and the 14C-PMMA method (in progress). [2] Sardini, P., Robinet, J., Siitari-Kauppi, M., Delay, F., and Hellmuth, K-H, (2007). On direct simulation of heterogeneous

  14. Magnetic fields in diffuse media

    CERN Document Server

    Pino, Elisabete; Melioli, Claudio

    2015-01-01

    This volume presents the current knowledge of magnetic fields in diffuse astrophysical media. Starting with an overview of 21st century instrumentation to observe astrophysical magnetic fields, the chapters cover observational techniques, origin of magnetic fields, magnetic turbulence, basic processes in magnetized fluids, the role of magnetic fields for cosmic rays, in the interstellar medium and for star formation. Written by a group of leading experts the book represents an excellent overview of the field. Nonspecialists will find sufficient background to enter the field and be able to appreciate the state of the art.

  15. Diffuse hemangioma of the colon

    International Nuclear Information System (INIS)

    Reis, J.; Caseiro-Alves, F.; Cruz, L.; Moreira, A.; Rebelo, O.

    1995-01-01

    We report two cases of diffuse hemangioma of the colon in adolescent patients. One patient had multiple phleboliths at the lower pelvis identified with plain radiographs of the abdomen. Several aspects were seen on double-contrast enema: luminal narrowing, colonic-wall thickening and submucosal colonic masses that changed in appearance with the degree of colonic distension. Angiography was inconclusive in one case. Use of CT and MR provided relevant information regarding the true extent of the disease, but MR was superior in demonstrating unequivocally the vascular nature of the lesions. (orig.)

  16. Bilateral diffuse uveal melanocytic proliferation

    DEFF Research Database (Denmark)

    Klemp, Kristian; Kiilgaard, Jens Folke; Heegaard, Steffen

    2017-01-01

    Bilateral diffuse uveal melanocytic proliferation (BDUMP) is a rare paraneoplastic intraocular disease that causes progressive visual loss in patients driven by an IgG factor associated with an underlying malignancy. Characteristic ocular findings include exudative retinal detachment, rapid...... cataract formation and uveal melanocytic tumours. The awareness and documentation of BDUMP has increased during the past decade, and the increasing amount of data collected demonstrates the effect of treatment with plasmapheresis and the value of diagnostic tools in BDUMP such as genetic and immunologic...

  17. Diffuse heterochromia of scalp hair.

    Science.gov (United States)

    Lee, W S; Lee, I W; Ahn, S K

    1996-11-01

    Heterochromia of hair is the presence of more than one distinct color of hair in the same person. A color difference between scalp hair and a mustache or sideburns is not uncommon. Pubic and axillary hair and eyebrows and eyelashes are often darker than scalp hair in a fair-haired person. Rarely, a circumscribed patch of hair of different colors occurs. However, diffuse heterochromia of black and red scalp hair has not been previously reported. We describe a father and son with this condition.

  18. An axisymmetric diffusion experiment for the determination of diffusion and sorption coefficients of rock samples.

    Science.gov (United States)

    Takeda, M; Hiratsuka, T; Ito, K; Finsterle, S

    2011-04-25

    Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an

  19. An asixymmetric diffusion experiment for the determination of diffusion and sorption coefficients of rock samples

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, M.; Hiratsuka, T.; Ito, K.; Finsterle, S.

    2011-02-01

    Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an

  20. Diffusion tensor MRI: clinical applications

    International Nuclear Information System (INIS)

    Meli, Francisco; Romero, Carlos; Carpintiero, Silvina; Salvatico, Rosana; Lambre, Hector; Vila, Jose

    2005-01-01

    Purpose: To evaluate the usefulness of diffusion-tensor imaging (DTI) on different neurological diseases, and to know if this technique shows additional information than conventional Magnetic Resonance Imaging (MRI). Materials and method: Eight patients, with neurological diseases (five patients with brain tumors, one with multiple sclerosis (MS), one with variant Creutzfeldt-Jakob disease (vCJD) and the other with delayed CO intoxication were evaluated. A MR scanner of 1.5 T was used and conventional sequences and DTI with twenty-five directions were done. Quantitative maps were gotten, where the fractional anisotropy (FA) through regions of interest (ROIs) in specific anatomic area were quantified (i.e.: internal and external capsules, frontal and temporal bundles, corpus fibers). Results: In the patients with brain tumors, there was a decrease of FA on intra and peritumoral fibers. Some of them had a disruption in their pattern. In patients with MS and CO intoxication, partial interruption along white matter bundles was demonstrated. However, a 'mismatch' between the findings of FLAIR, Diffusion-weighted images (DWI) and DTI, in the case of CO intoxication, was seen. Conclusions: DTI gave more information compared to conventional sequences about ultrastructural brain tissue in almost all the diseases above mentioned. Therefore, there is a work in progress about DTI acquisition, to evaluate a new technique, called tractography. (author)

  1. The foundations of diffusion revisited

    Energy Technology Data Exchange (ETDEWEB)

    Milligen, B. P. van; Carreras, B. A.; Sanchez, R.

    2005-07-01

    Fick's Law lies at the basis of the study of particle and heat transport in many fields of physics. The detailed analysis of transport in magnetically confined plasmas has revealed a very rich phenomenology, including some rather unusual behaviour, such as an unexpected scaling of confinement with system size, power degradation, stiff profiles, rapid transient phenomena (cold and heat pulses) and non-local behaviour, and profile peaking during off axis fueling. It has been extremely difficult to capture these phenomena in the standard transport modelling framework, i.e. local Fickian transport. Ad-hoc modifications of the standard transport paradigm have been proposed, but no unified framework has emerged that is capable of reproducing all phenomena. In the present talk, we review the foundations of the diffusive transport paradigm in terms of the Continuous Time Random Walk (CTRW), which is a generalization of standard Brownian motion. Using a simplified one-dimensional single-field model that incorporates a critical gradient mechanism, we will present a number of highly suggestive results, demonstrating that all mentioned phenomena arise in a natural fashion in this type of model. In addition, we discuss the fluid limit and show that the model produces a radially increasing effective diffusion and an inward directed pinch, very similar to the actual situation in confined plasmas. Finally, we will discuss the general relevance of this type of model for a more profound understanding of transport in magnetic confinement systems, while indicating future developments in this line of investigation. (Author)

  2. Mechanisms of impurity diffusion in rutile

    International Nuclear Information System (INIS)

    Peterson, N.L.; Sasaki, J.

    1984-01-01

    Tracer diffusion of 46 Sc, 51 Cr, 54 Mn, 59 Fe, 60 Co, 63 Ni, and 95 Zr, was measured as functions of crystal orientation, temperature, and oxygen partial pressure in rutile single crystals using the radioactive tracer sectioning technique. Compared to cation self-diffusion, divalent impurities (e.g., Co and Ni) diffuse extremely rapidly in TiO 2 and exhibit a large anisotropy in the diffusion behavior; divalent-impurity diffusion parallel to the c-axis is much larger than it is perpendicular to the c-axis. The diffusion of trivalent impurity ions (Sc and Cr) and tetravalent impurity ions (Zr) is similar to cation self-diffusion, as a function of temperature and of oxygen partial pressure. The divalent impurity ions Co and Ni apparently diffuse as interstitial ions along open channels parallel to the c-axis. The results suggest that Sc, Cr, and Zr ions diffuse by an interstitialcy mechanism involving the simultaneous and cooperative migration of tetravalent interstitial titanium ions and the tracer-impurity ions. Iron ions diffused both as divalent and as trivalent ions. 8 figures

  3. Bioresorbable scaffolds in the treatment of coronary artery disease

    OpenAIRE

    Zhang, Yaojun; Bourantas, Christos; Farooq, Vasim; Muramatsu, Takashi; Diletti, Roberto; Onuma, Yoshinobu; Garcia-Garcia, Hector; Serruys, Patrick

    2013-01-01

    textabstractDrug-eluting stents have reduced the risk of in-stent restenosis and have broadened the application in percutaneous coronary intervention in coronary artery disease. However, the concept of using a permanent metallic endovascular device to restore the patency of a stenotic artery has inherited pitfalls, namely the presence of a foreign body within the artery causing vascular inflammation, late complications such as restenosis and stent thrombosis, and impeding the restoration of t...

  4. Bioresorbable Scaffolds: Current Evidences in the Treatment of Coronary Artery Disease

    OpenAIRE

    Dave, Bhargav

    2016-01-01

    Percutaneous coronary revascularization strategies have gradually progressed over a period of last few decades. The advent of newer generation drug-eluting stents has significantly improved the outcomes of Percutaneous Coronary Intervention (PCI) by substantially reducing in-stent restenosis and stent thrombosis. However, vascular inflammation, restenosis, thrombosis, and neoatherosclerosis due to the permanent presence of a metallic foreign body within the artery limit their usage in complex...

  5. Classical diffusion: theory and simulation codes

    International Nuclear Information System (INIS)

    Grad, H.; Hu, P.N.

    1977-01-01

    The nonstandard mathematical and numerical problems which arise in classical diffusion theory upon reinsertion of the time derivative of the magnetic field (curl E not equal to 0) are discussed. The extension of classical diffusion theory to curl E not equal to 0 requires solution of a global boundary value problem before the surface averaged flux can be obtained. It also introduces coupling between plamsa diffusion and magnetic flux diffusion (the shin effect). The most effective method for treating Grad--Hogan classical diffusion was to introduce independent and dependent variables so as to eliminate the convection velocity (it can be computed afterwards). This procedure reduced the nonstandard, two dimensional problem to one with computation time only slightly more than for a one-dimensional diffusion problem. 23 references, 1 figure

  6. 2015 MICCAI Workshop on Computational Diffusion MRI

    CERN Document Server

    Ghosh, Aurobrata; Kaden, Enrico; Rathi, Yogesh; Reisert, Marco

    2016-01-01

    These Proceedings of the 2015 MICCAI Workshop “Computational Diffusion MRI” offer a snapshot of the current state of the art on a broad range of topics within the highly active and growing field of diffusion MRI. The topics vary from fundamental theoretical work on mathematical modeling, to the development and evaluation of robust algorithms, new computational methods applied to diffusion magnetic resonance imaging data, and applications in neuroscientific studies and clinical practice. Over the last decade interest in diffusion MRI has exploded. The technique provides unique insights into the microstructure of living tissue and enables in-vivo connectivity mapping of the brain. Computational techniques are key to the continued success and development of diffusion MRI and to its widespread transfer into clinical practice. New processing methods are essential for addressing issues at each stage of the diffusion MRI pipeline: acquisition, reconstruction, modeling and model fitting, image processing, fiber t...

  7. Radon progeny distribution in cylindrical diffusion chambers

    International Nuclear Information System (INIS)

    Pressyanov, Dobromir S.

    2008-01-01

    An algorithm to model the diffusion of radioactive decay chain atoms is presented. Exact mathematical solutions in cylindrical geometry are given. They are used to obtain expressions for the concentrations of 222 Rn progeny atoms in the volume and deposited on the wall surface in cylindrical diffusion chambers. The dependence of volume fractions of 222 Rn progeny and chamber sensitivity on the coefficient of diffusion of 222 Rn progeny atoms in air is modeled.

  8. Solute diffusion in Pu and Ce

    International Nuclear Information System (INIS)

    Marbach, Gabriel; Charissoux, Christian; Janot, Christian

    1976-01-01

    The diffusion rate of Co, Au and Ag in the bcc phases of Pu and Ce is studied. In the bcc delta phase of Pu, Au and Ag have the same diffusion rate that the matrix and Co is a very rapid solute. In the bcc phase of Ce, the diffusion coefficients of the three metals are remarkably high. This phenomenon is also observed in certain metallic matrices (Pb, Sn, [fr

  9. An Innovator's guidance to cost efficient diffusion

    OpenAIRE

    Hennschen, Lill; Andersen, Malene

    2012-01-01

    The project provides a practical relevance, based upon theoretical and empirical research, to cost efficient diffusion of an innovation. Theory of 'Diffusion of Innovations' by Everett Rogers, 'New rules of Marketing and PR' by David M.Scott, and 'Starting with why' by Simon Senik are the theoretical basis that contitutes this project. Here to a qualitative resarch method to answer the question of 'How to diffuse an innovation on a low budget?'

  10. Characterizing unsaturated diffusion in porous tuff gravel

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qinhong; Kneafsey, Timothy J.; Roberts, Jeffery J.; Tomutsa, Liviu; Wang, Joseph, S.Y.

    2003-11-12

    Evaluation of solute diffusion in unsaturated porous gravel is very important for investigations of contaminant transport and remediation, risk assessment, and waste disposal (for example, the potential high-level nuclear waste repository at Yucca Mountain, Nevada). For a porous aggregate medium such as granular tuff, the total water content is comprised of surface water and interior water. The surface water component (water film around grains and pendular water between the grain contacts) could serve as a predominant diffusion pathway. To investigate the extent to which surface water films and contact points affect solute diffusion in unsaturated gravel, we examined the configuration of water using x-ray computed tomography in partially saturated gravel, and made quantitative measurements of diffusion at multiple water contents using two different techniques. In the first, diffusion coefficients of potassium chloride in 2-4 mm granular tuff at multiple water contents were calculated from electrical conductivity measurements using the Nernst-Einstein equation. In the second, we used laser ablation with inductively coupled plasma-mass spectrometry to perform micro-scale mapping, allowing the measurement of diffusion coefficients for a mixture of chemical tracers for tuff cubes and tetrahedrons having two contact geometries (cube-cube and cube-tetrahedron). The x-ray computed tomography images show limited contact between grains, and this could hinder the pathways for diffusive transport. Experimental results show the critical role of surface water in controlling transport pathways and hence the magnitude of diffusion. Even with a bulk volumetric water content of 1.5%, the measured solute diffusion coefficient is as low as 1.5 x 10{sup -14} m{sup 2}/s for tuff gravel. Currently used diffusion models relating diffusion coefficients to total volumetric water content inadequately describe unsaturated diffusion behavior in porous gravel at very low water contents.

  11. Anomalous diffusion of fermions in superlattices

    International Nuclear Information System (INIS)

    Drozdz, S.; Okolowicz, J.; Srokowski, T.; Ploszajczak, M.

    1996-03-01

    Diffusion of fermions in the periodic two-dimensional lattice of fermions is studied. It is shown that effects connected with antisymmetrization of the wave function increase chaoticness of motion. Various types of anomalous diffusion, characterized by a power spectral analysis are found. The nonlocality of the Pauli potential destroys cantori in the phase space. Consequently, the diffusion process is dominated by long free paths and the power spectrum is logarithmic at small frequency limit. (author)

  12. Unstructured Polyhedral Mesh Thermal Radiation Diffusion

    International Nuclear Information System (INIS)

    Palmer, T.S.; Zika, M.R.; Madsen, N.K.

    2000-01-01

    Unstructured mesh particle transport and diffusion methods are gaining wider acceptance as mesh generation, scientific visualization and linear solvers improve. This paper describes an algorithm that is currently being used in the KULL code at Lawrence Livermore National Laboratory to solve the radiative transfer equations. The algorithm employs a point-centered diffusion discretization on arbitrary polyhedral meshes in 3D. We present the results of a few test problems to illustrate the capabilities of the radiation diffusion module

  13. Statistical Inference for Fractional Diffusion Processes

    CERN Document Server

    Rao, B L S Prakasa

    2010-01-01

    Statistical Inference for Fractional Diffusion Processes looks at statistical inference for stochastic processes modeled by stochastic differential equations driven by fractional Brownian motion. Other related processes, such as sequential inference, nonparametric and non parametric inference and parametric estimation are also discussed. The book will deal with Fractional Diffusion Processes (FDP) in relation to statistical influence for stochastic processes. The books main focus is on parametric and non parametric inference problems for fractional diffusion processes when a complete path of t

  14. Diffusion of spherical particles in microcavities

    OpenAIRE

    Imperio, A.; Padding, J. T.; Briels, W. J.

    2011-01-01

    The diffusive motion of a colloidal particle trapped inside a small cavity filled with fluid is reduced by hydrodynamic interactions with the confining walls. In this work, we study these wall effects on a spherical particle entrapped in a closed cylinder. We calculate the diffusion coefficient along the radial, azimuthal and axial direction for different particle positions. At all locations the diffusion is smaller than in a bulk fluid and it becomes anisotropic near the container's walls. W...

  15. Directed diffusion of reconstituting dimers

    Energy Technology Data Exchange (ETDEWEB)

    Barma, Mustansir [Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai 400005 (India); Grynberg, Marcelo D [Departamento de Fisica, Universidad Nacional de La Plata (1900) La Plata (Argentina); Stinchcombe, Robin B [Isaac Newton Institute for Mathematical Sciences, 20 Clarkson Road, Cambridge CB3 0EH (United Kingdom)

    2007-02-14

    We discuss the dynamical aspects of an asymmetric version of assisted diffusion of hard core particles on a ring studied by Menon et al (1997 J. Stat. Phys. 86 1237). The asymmetry brings in phenomena like kinematic waves and effects of the Kardar-Parisi-Zhang non-linearity, which combine with the feature of strongly broken ergodicity, a characteristic of the model. A central role is played by a single non-local invariant, the irreducible string, whose interplay with the driven motion of reconstituting dimers, arising from the assisted hopping, determines the asymptotic dynamics and scaling regimes. These are investigated both analytically and numerically through sector-dependent mappings to the asymmetric simple exclusion process.

  16. The double-diffusive modon

    Science.gov (United States)

    Radko, Timour

    Fully developed two-dimensional salt-finger convection is characterized by the appearance of coherent dipolar eddies which carry relatively fresh and cold fluid upward and salty and warm fluid downward. Such structures are prevalent in the regime in which density stratification is close to neutral and the salt-finger instability is extremely vigorous. The structure and translation velocities of modons are discussed in terms of the asymptotic expansion in which the background density ratio approaches unity. It is argued that the vertical salt flux is driven primarily by double-diffusive modons, which makes it possible to derive explicit expressions for the mixing rates of temperature and salinity as a function of their background gradients. Predictions of the proposed mixing model are successfully tested by direct numerical simulations.

  17. The diffuse cut-off

    International Nuclear Information System (INIS)

    2014-09-01

    After having recalled the interest of cut-off practices when consumption is higher than production (a cut-off operator turns out some sources of consumption), this publication more particularly addresses the practice of cut-off in the residential sector, also called diffused cut-off. This practice is based on a temporary reduction of electricity consumption in a great number of small sites (for example, a brief interruption of the electricity supply of radiators, hot water tanks, air conditioning devices in dwellings to reduce the total demand of an area). The three main modalities of valorisation of this cut-off power by the operator are presented. Advantages and drawbacks are discussed, and more particularly the impact of cut-off on thermal comfort

  18. Innovation and creativity : Beyond diffusion

    DEFF Research Database (Denmark)

    Michelsen, Anders Ib

    2009-01-01

    of postwar systems theory and introduce Castoriadis' philosophy as an interesting option in this regard. It proceeds in four parts: (a) First, it debates the limits of the commonplace metaphor of diffusion and adoption in today's debate on innovation. (b) Second, it will present aspects of Castoriadis......The article confronts Cornelius Castoriadis' philosophy of  'the imaginary institution of society' with issues of innovation in a knowledge society and outlines a new notion of innovation as creative organization. It will take a critical approach to innovation from a historical perspective......'s thought as an alternative, in particular his debate on imagination and the proto-institution of legein/teukhein — ordered action. (c) On this background it will treat a case from the Danish innovation industry, the firm Zentropa WorkZ's programme of 'Dramatic Innovation' as an interesting example...

  19. Word diffusion and climate science.

    Directory of Open Access Journals (Sweden)

    R Alexander Bentley

    Full Text Available As public and political debates often demonstrate, a substantial disjoint can exist between the findings of science and the impact it has on the public. Using climate-change science as a case example, we reconsider the role of scientists in the information-dissemination process, our hypothesis being that important keywords used in climate science follow "boom and bust" fashion cycles in public usage. Representing this public usage through extraordinary new data on word frequencies in books published up to the year 2008, we show that a classic two-parameter social-diffusion model closely fits the comings and goings of many keywords over generational or longer time scales. We suggest that the fashions of word usage contributes an empirical, possibly regular, correlate to the impact of climate science on society.

  20. Diffusion Indexes with Sparse Loadings

    DEFF Research Database (Denmark)

    Kristensen, Johannes Tang

    to the problem by using the LASSO as a variable selection method to choose between the possible variables and thus obtain sparse loadings from which factors or diffusion indexes can be formed. This allows us to build a more parsimonious factor model which is better suited for forecasting compared......The use of large-dimensional factor models in forecasting has received much attention in the literature with the consensus being that improvements on forecasts can be achieved when comparing with standard models. However, recent contributions in the literature have demonstrated that care needs...... to the traditional principal components (PC) approach.We provide an asymptotic analysis of the estimator and illustrate its merits empirically in a forecasting experiment based on US macroeconomic data. Overall we find that compared to PC we obtain improvements in forecasting accuracy and thus find...

  1. Diffusion Indexes With Sparse Loadings

    DEFF Research Database (Denmark)

    Kristensen, Johannes Tang

    2017-01-01

    The use of large-dimensional factor models in forecasting has received much attention in the literature with the consensus being that improvements on forecasts can be achieved when comparing with standard models. However, recent contributions in the literature have demonstrated that care needs...... to the problem by using the least absolute shrinkage and selection operator (LASSO) as a variable selection method to choose between the possible variables and thus obtain sparse loadings from which factors or diffusion indexes can be formed. This allows us to build a more parsimonious factor model...... that is better suited for forecasting compared to the traditional principal components (PC) approach. We provide an asymptotic analysis of the estimator and illustrate its merits empirically in a forecasting experiment based on U.S. macroeconomic data. Overall we find that compared to PC we obtain improvements...

  2. Diffusion in condensed matter methods, materials, models

    CERN Document Server

    Kärger, Jörg

    2005-01-01

    Diffusion as the process of particle transport due to stochastic movement is a phenomenon of crucial relevance for a large variety of processes and materials. This comprehensive, handbook- style survey of diffusion in condensed matter gives detailed insight into diffusion as the process of particle transport due to stochastic movement. Leading experts in the field describe in 23 chapters the different aspects of diffusion, covering microscopic and macroscopic experimental techniques and exemplary results for various classes of solids, liquids and interfaces as well as several theoretical concepts and models. Students and scientists in physics, chemistry, materials science, and biology will benefit from this detailed compilation.

  3. Enhancing Rotational Diffusion Using Oscillatory Shear

    KAUST Repository

    Leahy, Brian D.

    2013-05-29

    Taylor dispersion - shear-induced enhancement of translational diffusion - is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle\\'s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids. © 2013 American Physical Society.

  4. Industrial diffusion models and technological standardization

    International Nuclear Information System (INIS)

    Carrillo-Hermosilla, J.

    2007-01-01

    Conventional models of technology diffusion have typically focused on the question of the rate of diffusion at which one new technology is fully adopted. The model described here provides a broader approach, from the perspective the extension of the diffusion of multiple technologies, and the related phenomenon of standardization. Moreover, most conventional research has characterized the diffusion process in terms of technology attributes or adopting firms attributes. Alternatively, we propose here a wide-ranging and consistent taxonomy of the relationships between the circumstances of an industry and the attributes of the technology standardization processes taking place within it. (Author) 100 refs

  5. Pressure effect on grain boundary diffusion

    International Nuclear Information System (INIS)

    Smirnova, E.S.; Chuvil'deev, V.N.

    1997-01-01

    The influence of hydrostatic pressure on grain boundary diffusion and grain boundary migration in metallic materials is theoretically investigated. The model is suggested that permits describing changes in activation energy of grain boundary self-diffusion and diffusion permeability of grain boundaries under hydrostatic pressure. The model is based on the ideas about island-type structure of grain boundaries as well as linear relationship of variations in grain boundary free volume to hydrostatic pressure value. Comparison of theoretical data with experimental ones for a number of metals and alloys (α-Zr, Sn-Ge, Cu-In with Co, In, Al as diffusing elements) shows a qualitative agreement

  6. Biomimetic phantom for cardiac diffusion MRI.

    Science.gov (United States)

    Teh, Irvin; Zhou, Feng-Lei; Hubbard Cristinacce, Penny L; Parker, Geoffrey J M; Schneider, Jürgen E

    2016-03-01

    Diffusion magnetic resonance imaging (MRI) is increasingly used to characterize cardiac tissue microstructure, necessitating the use of physiologically relevant phantoms for methods development. Existing phantoms are generally simplistic and mostly simulate diffusion in the brain. Thus, there is a need for phantoms mimicking diffusion in cardiac tissue. A biomimetic phantom composed of hollow microfibers generated using co-electrospinning was developed to mimic myocardial diffusion properties and fiber and sheet orientations. Diffusion tensor imaging was carried out at monthly intervals over 4 months at 9.4T. 3D fiber tracking was performed using the phantom and compared with fiber tracking in an ex vivo rat heart. The mean apparent diffusion coefficient and fractional anisotropy of the phantom remained stable over the 4-month period, with mean values of 7.53 ± 0.16 × 10(-4) mm(2) /s and 0.388 ± 0.007, respectively. Fiber tracking of the 1st and 3rd eigenvectors generated analogous results to the fiber and sheet-normal direction respectively, found in the left ventricular myocardium. A biomimetic phantom simulating diffusion in the heart was designed and built. This could aid development and validation of novel diffusion MRI methods for investigating cardiac microstructure, decrease the number of animals and patients needed for methods development, and improve quality control in longitudinal and multicenter cardiac diffusion MRI studies. © 2015 The Authors Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

  7. Diffusion mechanisms in grain boundaries in solids

    International Nuclear Information System (INIS)

    Peterson, N.L.

    1982-01-01

    A critical review is given of our current knowledge of grain-boundary diffusion in solids. A pipe mechanism of diffusion based on the well-established dislocation model seems most appropriate for small-angle boundaries. Open channels, which have atomic configurations somewhat like dislocation cores, probably play a major role in large-angle grain-boundary diffusion. Dissociated dislocations and stacking faults are not efficient paths for grain-boundary diffusion. The diffusion and computer modeling experiments are consistent with a vacancy mechanism of diffusion by a rather well-localized vacancy. The effective width of a boundary for grain-boundary diffusion is about two atomic planes. These general features of grain-boundary diffusion, deduced primarily from experiments on metals, are thought to be equally applicable for pure ceramic solids. The ionic character of many ceramic oxides may cause some differences in grain-boundary structure from that observed in metals, resulting in changes in grain-boundary diffusion behavior. 72 references, 5 figures

  8. Accounting for diffusion in agent based models of reaction-diffusion systems with application to cytoskeletal diffusion.

    Science.gov (United States)

    Azimi, Mohammad; Jamali, Yousef; Mofrad, Mohammad R K

    2011-01-01

    Diffusion plays a key role in many biochemical reaction systems seen in nature. Scenarios where diffusion behavior is critical can be seen in the cell and subcellular compartments where molecular crowding limits the interaction between particles. We investigate the application of a computational method for modeling the diffusion of molecules and macromolecules in three-dimensional solutions using agent based modeling. This method allows for realistic modeling of a system of particles with different properties such as size, diffusion coefficients, and affinity as well as the environment properties such as viscosity and geometry. Simulations using these movement probabilities yield behavior that mimics natural diffusion. Using this modeling framework, we simulate the effects of molecular crowding on effective diffusion and have validated the results of our model using Langevin dynamics simulations and note that they are in good agreement with previous experimental data. Furthermore, we investigate an extension of this framework where single discrete cells can contain multiple particles of varying size in an effort to highlight errors that can arise from discretization that lead to the unnatural behavior of particles undergoing diffusion. Subsequently, we explore various algorithms that differ in how they handle the movement of multiple particles per cell and suggest an algorithm that properly accommodates multiple particles of various sizes per cell that can replicate the natural behavior of these particles diffusing. Finally, we use the present modeling framework to investigate the effect of structural geometry on the directionality of diffusion in the cell cytoskeleton with the observation that parallel orientation in the structural geometry of actin filaments of filopodia and the branched structure of lamellipodia can give directionality to diffusion at the filopodia-lamellipodia interface.

  9. Diffusion Modeling: A Study of the Diffusion of “Jatropha Curcas ...

    African Journals Online (AJOL)

    Consequently, the study recommended the use of diffusion networks which integrate interpersonal networks, and multimedia strategies for the effective diffusion of innovation such as Jacodiesel in Adamawa State and other parts of the country. Keywords: Sustainability, Diffusion, Innovation, Communicative Influence, ...

  10. Chloride diffusion in partially saturated cementitious material

    DEFF Research Database (Denmark)

    Nielsen, Erik Pram; Geiker, Mette Rica

    2003-01-01

    The paper proposes a combined application of composite theory and Powers' model for microstructural development for the estimation of the diffusion coefficient as a function of the moisture content of a defect-free cementitious material. Measurements of chloride diffusion in mortar samples (440 kg...

  11. Gas phase thermal diffusion of stable isotopes

    International Nuclear Information System (INIS)

    Eck, C.F.

    1979-01-01

    The separation of stable isotopes at Mound Facility is reviewed from a historical perspective. The historical development of thermal diffusion from a laboratory process to a separation facility that handles all the noble gases is described. In addition, elementary thermal diffusion theory and elementary cascade theory are presented along with a brief review of the uses of stable isotopes

  12. Diffusion and scattering in multifractal clouds

    Energy Technology Data Exchange (ETDEWEB)

    Lovejoy, S. [McGill Univ., Montreal, Quebec (Canada); Schertzer, D. [Universite Pierre et Marie Curie, Paris (France); Waston, B. [St. Lawrence Univ., Canton, NY (United States)] [and others

    1996-04-01

    This paper describes investigations of radiative properties of multifractal clouds using two different approaches. In the first, diffusion is considered by examining the scaling properties of one dimensional random walks on media with multifractal diffusivities. The second approach considers the scattering statistics associated with radiative transport.

  13. Depolarization of diffusing spins by paramagnetic impurities

    International Nuclear Information System (INIS)

    Schillaci, M.E.; Hutson, R.L.; Heffner, R.H.; Leon, M.; Dodds, S.A.; Estle, T.L.

    1980-01-01

    The depolarization of diffusing spins (muons) interacting with dilute paramagnetic impurities in a solid was studied using a simple computational model which properly treats the muon motion and preserves correct muon-impurity distances. Long-range (dipolar) and nearest-neighbor (contact) interactions are treated together. Diffusion parameters are deduced and model comparisons made for AuGd

  14. High resolution CT in diffuse lung disease

    International Nuclear Information System (INIS)

    Webb, W.R.

    1995-01-01

    High resolution CT (computerized tomography) was discussed in detail. The conclusions were HRCT is able to define lung anatomy at the secondary lobular level and define a variety of abnormalities in patients with diffuse lung diseases. Evidence from numerous studies indicates that HRCT can play a major role in the assessment of diffuse infiltrative lung disease and is indicate clinically (95 refs.)

  15. Diffuse Alveolar Hemorrhage Associated with Warfarin Therapy

    OpenAIRE

    Kaya, Bülent; Yildiz, Ibrahim; Baha, Reshat Mehmet; Zeytun, Neslihan Ebru Eryaşar; Yetisgen, Azize

    2015-01-01

    Diffuse alveolar hemorrhage (DAH) is a life-threatening clinical pathologic syndrome caused by a variety of diseases. We report a case of DAH related to therapy of warfarin use. In this case report, we present the diffuse alveolar hemorrhage case as a rare and life-threatening complication of warfarin.

  16. Diffuse Alveolar Hemorrhage Associated with Warfarin Therapy.

    Science.gov (United States)

    Kaya, Bülent; Yildiz, Ibrahim; Baha, Reshat Mehmet; Zeytun, Neslihan Ebru Eryaşar; Yetisgen, Azize

    2015-01-01

    Diffuse alveolar hemorrhage (DAH) is a life-threatening clinical pathologic syndrome caused by a variety of diseases. We report a case of DAH related to therapy of warfarin use. In this case report, we present the diffuse alveolar hemorrhage case as a rare and life-threatening complication of warfarin.

  17. Diffuse Alveolar Hemorrhage Associated with Warfarin Therapy

    Directory of Open Access Journals (Sweden)

    Bülent Kaya

    2015-01-01

    Full Text Available Diffuse alveolar hemorrhage (DAH is a life-threatening clinical pathologic syndrome caused by a variety of diseases. We report a case of DAH related to therapy of warfarin use. In this case report, we present the diffuse alveolar hemorrhage case as a rare and life-threatening complication of warfarin.

  18. NEEDED RESEARCH ON DIFFUSION WITHIN EDUCATIONAL ORGANIZATIONS.

    Science.gov (United States)

    JAIN, NEMI C.; ROGERS, EVERETT M.

    IN SPITE OF THE VOLUME OF RESEARCH ATTENTION DEVOTED TO THE DIFFUSION OF INNOVATIONS, RELATIVELY LITTLE EMPHASIS HAS BEEN PLACED UPON DIFFUSION WITHIN ORGANIZATIONAL STRUCTURES. METHODOLOGICALLY, RELATIONAL ANALYSIS IN WHICH THE UNIT OF ANALYSIS IS A TWO-PERSON INTERACTING PAIR, A MULTIPLE PERSON COMMUNICATION CHAIN, OR CLIQUES OR SUBSYSTEMS IS…

  19. Finite-difference schemes for anisotropic diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Es, Bram van, E-mail: es@cwi.nl [Centrum Wiskunde and Informatica, P.O. Box 94079, 1090GB Amsterdam (Netherlands); FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands); Koren, Barry [Eindhoven University of Technology (Netherlands); Blank, Hugo J. de [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands)

    2014-09-01

    In fusion plasmas diffusion tensors are extremely anisotropic due to the high temperature and large magnetic field strength. This causes diffusion, heat conduction, and viscous momentum loss, to effectively be aligned with the magnetic field lines. This alignment leads to different values for the respective diffusive coefficients in the magnetic field direction and in the perpendicular direction, to the extent that heat diffusion coefficients can be up to 10{sup 12} times larger in the parallel direction than in the perpendicular direction. This anisotropy puts stringent requirements on the numerical methods used to approximate the MHD-equations since any misalignment of the grid may cause the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. Currently the common approach is to apply magnetic field-aligned coordinates, an approach that automatically takes care of the directionality of the diffusive coefficients. This approach runs into problems at x-points and at points where there is magnetic re-connection, since this causes local non-alignment. It is therefore useful to consider numerical schemes that are tolerant to the misalignment of the grid with the magnetic field lines, both to improve existing methods and to help open the possibility of applying regular non-aligned grids. To investigate this, in this paper several discretization schemes are developed and applied to the anisotropic heat diffusion equation on a non-aligned grid.

  20. Acetylene diffusion in Na-Y zeolite

    Indian Academy of Sciences (India)

    The diffusion constant, residence time between jumps and root mean square jump length are determined. Keywords. Porous materials; diffusion; neutron scattering. ... of diameter ~11.8 Å. The pores are interconnected through windows of diameter. ~7.8 Å. Recent molecular dynamics (MD) simulation studies [6] show a ...

  1. Mid infrared upconversion spectroscopy using diffuse reflectance

    DEFF Research Database (Denmark)

    Sanders, Nicolai Højer; Kehlet, Louis M.; Dam, Jeppe Seidelin

    2014-01-01

    specifically that upconversion methods can be deployed using a diffuse reflectance setup where the test sample is irradiated by a thermal light source, i.e. a globar. The diffuse reflectance geometry is particularly well suited when a transmission setup cannot be used. This situation may happen for highly...

  2. Diffusion bonding from antiquity to present times

    CERN Document Server

    Mathot, S

    2004-01-01

    This paper describes attempts made to improve diffusion bonding procedures based on antique processes as granulation and filigree. Two modern procedures implying diffusion of cadmium and silicon respectively are reported. The results obtained with PIXE and NRA using nuclear microprobe are discussed. This paper concludes with a comparison of these bonding techniques and some other modern methods with the antique procedures.

  3. Imaging features of diffuse pulmonary hemorrhage

    International Nuclear Information System (INIS)

    Schmit, M.; Vogel, W.; Horger, M.

    2006-01-01

    There are diverse etiologies of diffuse pulmonary hemorrhage, so specific diagnosis may be difficult. Conventional radiography tends to be misleading as hemoptysis may lacking in patients with hemorrhagic anemia. Diffuse pulmonary hemorrhage should be differentiated from focal pulmonary hemorrhage resulting from chronic bronchitis, bronchiectasis, active infection (tuberculosis) neoplasia, trauma, or embolism. (orig.)

  4. Derivation of the neutron diffusion equation

    International Nuclear Information System (INIS)

    Mika, J.R.; Banasiak, J.

    1994-01-01

    We discuss the diffusion equation as an asymptotic limit of the neutron transport equation for large scattering cross sections. We show that the classical asymptotic expansion procedure does not lead to the diffusion equation and present two modified approaches to overcome this difficulty. The effect of the initial layer is also discussed. (authors). 9 refs

  5. Undergraduate Laboratory Module on Skin Diffusion

    Science.gov (United States)

    Norman, James J.; Andrews, Samantha N.; Prausnitz, Mark R.

    2011-01-01

    To introduce students to an application of chemical engineering directly related to human health, we developed an experiment for the unit operations laboratory at Georgia Tech examining diffusion across cadaver skin in the context of transdermal drug delivery. In this laboratory module, students prepare mouse skin samples, set up diffusion cells…

  6. Self-diffusion in remodeling and growth

    KAUST Repository

    Epstein, Marcelo

    2011-07-16

    Self-diffusion, or the flux of mass of a single species within itself, is viewed as an independent phenomenon amenable to treatment by the introduction of an auxiliary field of diffusion velocities. The theory is shown to be heuristically derivable as a limiting case of that of an ordinary binary mixture. © 2011 Springer Basel AG.

  7. Multicomponent diffusivities from the free volume theory

    NARCIS (Netherlands)

    Wesselingh, J.A; Bollen, A.M

    In this paper the free volume theory of diffusion is extended to multicomponent mixtures. The free volume is taken to be accessible for any component according to its surface. fraction. The resulting equations predict multicomponent (Maxwell-Stefan) diffusivities in simple liquid mixtures from pure

  8. Self-diffusion on copper surfaces

    DEFF Research Database (Denmark)

    Hansen, L.; Stoltze, Per; Jacobsen, Karsten Wedel

    1991-01-01

    The diffusion paths and activation energies of a Cu adatom on Cu(100), Cu(111), and Cu(110) are studied using the effective-medium theory to calculate the energetics. For the (100) and (110) faces, diffusion via an exchange mechanism is found to be important. The transition state for these paths ...

  9. Diffuse sound field: challenges and misconceptions

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2016-01-01

    tremendously in different chambers because the chambers are non-diffuse in variously different ways. Therefore, good objective measures that can quantify the degree of diffusion and potentially indicate how to fix such problems in reverberation chambers are needed. Acousticians often blend the concept...

  10. Integrated Temperature Sensors based on Heat Diffusion

    NARCIS (Netherlands)

    Van Vroonhoven, C.P.L.

    2015-01-01

    This thesis describes the theory, design and implementation of a new class of integrated temperature sensors, based on heat diffusion. In such sensors, temperature is sensed by measuring the time it takes for heat to diffuse through silicon. An on-chip thermal delay can be determined by geometry and

  11. MR diffusion imaging of human intracranial tumours

    DEFF Research Database (Denmark)

    Krabbe, K; Gideon, P; Wagn, P

    1997-01-01

    We used MRI for in vivo measurement of brain water self-diffusion in patients with intracranial tumours. The study included 28 patients (12 with high-grade and 3 with low-grade gliomas, 7 with metastases, 5 with meningiomas and 1 with a cerebral abscess). Apparent diffusion coefficients (ADC) wer...

  12. Multicomponent diffusion in two-temperature magnetohydrodynamics

    International Nuclear Information System (INIS)

    Ramshaw, J.D.; Chang, C.H.

    1996-01-01

    A recent hydrodynamic theory of multicomponent diffusion in multitemperature gas mixtures [J. D. Ramshaw, J. Non-Equilib. Thermodyn. 18, 121 (1993)] is generalized to include the velocity-dependent Lorentz force on charged species in a magnetic field B. This generalization is used to extend a previous treatment of ambipolar diffusion in two-temperature multicomponent plasmas [J. D. Ramshaw and C. H. Chang, Plasma Chem. Plasma Process. 13, 489 (1993)] to situations in which B and the electrical current density are nonzero. General expressions are thereby derived for the species diffusion fluxes, including thermal diffusion, in both single- and two-temperature multicomponent magnetohydrodynamics (MHD). It is shown that the usual zero-field form of the Stefan-Maxwell equations can be preserved in the presence of B by introducing generalized binary diffusion tensors dependent on B. A self-consistent effective binary diffusion approximation is presented that provides explicit approximate expressions for the diffusion fluxes. Simplifications due to the small electron mass are exploited to obtain an ideal MHD description in which the electron diffusion coefficients drop out, resistive effects vanish, and the electric field reduces to a particularly simple form. This description should be well suited for numerical calculations. copyright 1996 The American Physical Society

  13. Universality in edge-source diffusion dynamics

    DEFF Research Database (Denmark)

    Mortensen, Asger; Okkels, Fridolin; Bruus, Henrik

    2006-01-01

    We show that in edge-source diffusion dynamics the integrated concentration N(t) has a universal dependence with a characteristic time scale tau=(A/P)(2)pi/(4D), where D is the diffusion constant while A and P are the cross-sectional area and perimeter of the domain, respectively. For the short...

  14. Global Banning of a Diffused Controversial Practice

    DEFF Research Database (Denmark)

    Gurses, Kerem; Giones, Ferran; Mehta, Kandarpkumar

    2017-01-01

    We study the deinstitutionalization of a controversial practice that had previously reached a level of international diffusion. We draw on international diffusion and deinstitutionalization theory to study the emergence and diffusion of the third-party ownership practice in the soccer industry. We...... use an inductive case study combining archival and interview data to study the determinants of the international diffusion of a controversial practice at a global scale, the contestation, and finally the deinstitutionalization process that resulted from the ban of the practice. We find...... that the opacity of the practice can be a diffusion driver, locally and at the international level, nevertheless the opacity also may lead to different meaning creation attempts and potential discursive battles between actors, and eventually to deinstitutionalization of the practice. This article advances our...

  15. Changes in brain water diffusion during childhood

    Energy Technology Data Exchange (ETDEWEB)

    Morriss, M.C.; Zimmerman, R.A.; Bilaniuk, L.T.; Hunter, J.V.; Haselgrove, J.C. [Children' s Hospital of Philadelphia (United States)

    1999-12-01

    We studied the changes in brain water diffusion in childhood as seen on diffusion-weighted MRI in 30 children from 1 day of life to 17 years to provide a data base and to investigate the correlation of diffusion changes with known patterns of white matter maturation. The apparent diffusion coefficient (ADC) and apparent anisotropy (AA) were calculated in numerous regions of the brain to include major white matter tracts and gray matter. ADC and AA values were directly related to the structural maturity and compactness of the white matter tracts and changed with aging in a way that predated early myelination markers such as signal change on T1- or T2-weighted images. Diffusion of water is sensitive to structural changes in the brain such as white matter maturation and may be useful in investigating white matter disorders. (orig.)

  16. Principles and limitations of NMR diffusion measurements

    Directory of Open Access Journals (Sweden)

    Hrabe Jan

    2007-01-01

    Full Text Available Diffusion spectroscopy, imaging and particularly diffusion tensor imaging have become popular thanks to their numerous clinical and research applications which span from brain stroke evaluation to fiber tracking. With a few exceptions, these methods are rooted in the classic Stejskal-Tanner formula for the diffusion-attenuated signal, usually obtained by solving the Bloch-Torrey partial differential equations. Here we derive the Stejskal-Tanner formula in the simplest possible manner, avoiding integrals and differential equations. This approach makes it easy to understand the origin of the diffusion signal attenuation, the effects of various diffusion sequence parameters, and also the numerous important pitfalls, which are discussed in the last section.

  17. Physical bases for diffusion welding processes optimization

    International Nuclear Information System (INIS)

    Bulygina, S.M.; Berber, N.N.; Mukhambetov, D.G.

    1999-01-01

    One of wide-spread method of different materials joint is diffusion welding. It has being brought off at the expense of mutual diffusion of atoms of contacting surfaces under long-duration curing at its heating and compression. Welding regime in dependence from properties of welding details is defining of three parameters: temperature, pressure, time. Problem of diffusion welding optimization concludes in determination less values of these parameters, complying with requirements for quality of welded joint. In the work experiments on diffusion welding for calculated temperature and for given surface's roughness were carried out. Tests conduct on samples of iron and iron-nickel alloy with size 1·1·1 cm 3 . Optimal regime of diffusion welding of examined samples in vacuum is defined. It includes compression of welding samples, heating, isothermal holding at temperature 650 deg C during 0.5 h and affords the required homogeneity of joint

  18. Nuclear diffuseness as a degree of freedom

    International Nuclear Information System (INIS)

    Myers, W.D.; Swiatecki, W.J.

    1998-01-01

    The response of the nuclear energy to changes in neutron and proton surface diffusenesses is investigated using the Thomas-Fermi model. Algebraic expressions are provided for the energy cost of changing the two diffusenesses away from their equilibrium values. This will make it possible to generalize the macroscopic-microscopic calculations of nuclear masses and deformation energies by the inclusion of the neutron and proton diffusenesses as degrees of freedom (to be varied along with the shape degrees of freedom). One result, which is suggested by the relatively low cost in macroscopic energy of increasing the diffuseness of a heavy nucleus by 10% (about 4 MeV), is that superheavy nuclei near Z=126, N=184 may have a fair chance of becoming stabilized by shell effects. An appendix introduces an improved measure of surface diffuseness, with certain advantages over the conventional Suessmann width b. copyright 1998 The American Physical Society

  19. Nuclear diffuseness as a degree of freedom

    Science.gov (United States)

    Myers, W. D.; ŚwiaŢecki, W. J.

    1998-12-01

    The response of the nuclear energy to changes in neutron and proton surface diffusenesses is investigated using the Thomas-Fermi model. Algebraic expressions are provided for the energy cost of changing the two diffusenesses away from their equilibrium values. This will make it possible to generalize the macroscopic-microscopic calculations of nuclear masses and deformation energies by the inclusion of the neutron and proton diffusenesses as degrees of freedom (to be varied along with the shape degrees of freedom). One result, which is suggested by the relatively low cost in macroscopic energy of increasing the diffuseness of a heavy nucleus by 10% (about 4 MeV), is that superheavy nuclei near Z=126, N=184 may have a fair chance of becoming stabilized by shell effects. An appendix introduces an improved measure of surface diffuseness, with certain advantages over the conventional Süssmann width b.

  20. Solid-state diffusion in amorphous zirconolite

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C.; Dove, M. T.; Trachenko, K. [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Zarkadoula, E. [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6138 (United States); Todorov, I. T. [STFC Daresbury Laboratory, Warrington WA4 1EP (United Kingdom); Geisler, T. [Steinmann-Institut für Geologie, Mineralogie und Paläontologie, University of Bonn, D-53115 Bonn (Germany); Brazhkin, V. V. [Institute for High Pressure Physics, RAS, 142190 Moscow (Russian Federation)

    2014-11-14

    We discuss how structural disorder and amorphization affect solid-state diffusion, and consider zirconolite as a currently important case study. By performing extensive molecular dynamics simulations, we disentangle the effects of amorphization and density, and show that a profound increase of solid-state diffusion takes place as a result of amorphization. Importantly, this can take place at the same density as in the crystal, representing an interesting general insight regarding solid-state diffusion. We find that decreasing the density in the amorphous system increases pre-factors of diffusion constants, but does not change the activation energy in the density range considered. We also find that atomic species in zirconolite are affected differently by amorphization and density change. Our microscopic insights are relevant for understanding how solid-state diffusion changes due to disorder and for building predictive models of operation of materials to be used to encapsulate nuclear waste.

  1. Silicon Self-Diffusion in Isotope Heterostructures

    International Nuclear Information System (INIS)

    Bracht, H.; Haller, E.E.; Clark-Phelps, R.

    1998-01-01

    Self-diffusion of silicon is measured between 855 and 1388thinsp degree C in highly isotopically enriched 28 Si layers. The profiles of 29 Si and 30 Si are determined by secondary ion mass spectrometry. Temperature dependence of the self-diffusion coefficients is accurately described over seven orders of magnitude with one diffusion enthalpy of 4.75thinspthinspeV. This single enthalpy indicates that self-interstitials dominate self-diffusion. The high accuracy of our data enables us to estimate an upper bound for the vacancy-assisted diffusion enthalpy of 4.14thinspthinspeV, which agrees with recent theoretical calculations. copyright 1998 The American Physical Society

  2. Carrier illumination measurement of dopant lateral diffusion

    International Nuclear Information System (INIS)

    Budiarto, E.; Segovia, M.; Borden, P.; Felch, S.

    2005-01-01

    This paper describes the application of the carrier illumination technique to non-destructively measure the lateral diffusion of implanted dopants after annealing. Experiments to validate the feasibility of this method employed test structures with a constant line width of 300 nm and varying undoped spaces of 100-5000 nm. The test patterns were implanted with a p-type dopant and annealed in a 3 x 3 matrix. For each implant condition, the measured lateral diffusion was found to increase with annealing temperature, as expected. More interestingly, the lateral diffusion was not observed to relate to the vertical diffusion by a fixed proportionality factor, as is usually assumed. The ratio of lateral to vertical diffusion varies with annealing temperature, with a trend that depends on the implant condition

  3. Basic consideration of diffusion/perfusion imaging

    International Nuclear Information System (INIS)

    Tamagawa, Yoichi; Kimura, Hirohiko; Matsuda, Tsuyoshi; Kawamura, Yasutaka; Nakatsugawa, Shigekazu; Ishii, Yasushi; Sakuma, Hajime; Tsukamoto, Tetsuji.

    1990-01-01

    In magnetic resonance imaging (MRI), microscopic motion of biological system such as molecular diffusion of water and microcirculation of blood in the capillary network (perfusion) has been proposed to cause signal attenuation as an intravoxel incoherent motion (IVIM). Quantitative imaging of the IVIM phenomenon was attempted to generate from a set of spin-echo (SE) sequences with or without sensitization by motion probing gradient (MPG). The IVIM imaging is characterized by a parameter, apparent diffusion coefficient (ADC), which is an integration of both the diffusion and the perfusion factor on voxel-by-voxel basis. Hard ware was adjusted to avoid image artifact mainly produced by eddy current. Feasibility of the method was tested using bottle phantom filled with water at different temperature and acetone, and the calculated ADC values of these media corresponded well with accepted values of diffusion. The method was then applied to biological system to investigate mutual participation of diffusion/perfusion on the ADC value. The result of tumor model born on nude mouse suggested considerable participation of perfusion factor which immediately disappeared after sacrificing the animal. Meanwhile, lower value of sacrificed tissue without microcirculation was suggested to have some restriction of diffusion factor by biological tissue. To substantiate the restriction effect on the diffusion, a series of observation have made on a fiber phantom, stalk of celory with botanical fibers and human brain with nerve fibers, in applying unidirectional MPG along the course of these banch of fiber system. The directional restriction effect of diffusion along the course of fiber (diffusion anisotrophy) was clearly visualized as directional change of ADC value. The present method for tissue characterization by diffusion/perfusion on microscopic level will provide a new insight for evaluation of functional derangement in human brain and other organs. (author)

  4. Diffusion tensor imaging in spinal cord compression

    International Nuclear Information System (INIS)

    Wang, Wei; Qin, Wen; Hao, Nanxin; Wang, Yibin; Zong, Genlin

    2012-01-01

    Background Although diffusion tensor imaging has been successfully applied in brain research for decades, several main difficulties have hindered its extended utilization in spinal cord imaging. Purpose To assess the feasibility and clinical value of diffusion tensor imaging and tractography for evaluating chronic spinal cord compression. Material and Methods Single-shot spin-echo echo-planar DT sequences were scanned in 42 spinal cord compression patients and 49 healthy volunteers. The mean values of the apparent diffusion coefficient and fractional anisotropy were measured in region of interest at the cervical and lower thoracic spinal cord. The patients were divided into two groups according to the high signal on T2WI (the SCC-HI group and the SCC-nHI group for with or without high signal). A one-way ANOVA was used. Diffusion tensor tractography was used to visualize the morphological features of normal and impaired white matter. Results There were no statistically significant differences in the apparent diffusion coefficient and fractional anisotropy values between the different spinal cord segments of the normal subjects. All of the patients in the SCC-HI group had increased apparent diffusion coefficient values and decreased fractional anisotropy values at the lesion level compared to the normal controls. However, there were no statistically significant diffusion index differences between the SCC-nHI group and the normal controls. In the diffusion tensor imaging maps, the normal spinal cord sections were depicted as fiber tracts that were color-encoded to a cephalocaudal orientation. The diffusion tensor images were compressed to different degrees in all of the patients. Conclusion Diffusion tensor imaging and tractography are promising methods for visualizing spinal cord tracts and can provide additional information in clinical studies in spinal cord compression

  5. Study of uranium-titanium diffusion

    International Nuclear Information System (INIS)

    Adda, Y.; Philibert, J.

    1959-01-01

    In the overall scheme of research on the chemical diffusion of uranium and the transition metals we have studied the uranium-titanium system. The diffusion couples are prepared by welding together small plates of uranium and titanium under pressure, using a technique already described by us. After diffusion under vacuum, polished sections of the samples were micro-graphically examined. This inspection showed that intergranular diffusion occurred at temperatures below 650 deg. C. At higher temperatures, the diffusion occurred uniquely throughout the volume of the metal, and the diffusion zone appeared as a succession of micro-graphically distinguishable bands. Study of the rate of increase of these corresponding 'penetration coefficients'. In addition, we have observed important variations in microhardness within the diffusion zone, we have tried to relate these variations to the variation of concentration. This is measured with the Castaing microprobe. We have thus accurately established the concentration-penetration curves for temperatures between 950 and 1075 deg. C. From these curves, we have calculated the diffusion coefficient D as a function of the concentration using Matano's method. At all temperatures, D(c) curve has a U form as for the U-Zr system. The activation energy has a maximum value of 42 kcal/g atom at an atomic concentration of 0,5. Even though we have rarely seen pores in the diffusion zone, we have nevertheless observed an important Kirkendall-effect by studying the displacements x i of the interface using tungsten wires as markers. These displacements can be expressed as a function of time and temperature by the equation: x i = 0,9 t 1/2 exp ( - 14600/(RT)). Finally, using Darken's equations we calculated the intrinsic diffusion coefficients Du and Dti as well as the corresponding activation energies. These energies are similar (QU = 38,5 and QTi = 40 kcal/at. g) and also almost the same as those found for the U-Zr system. (author) [fr

  6. Ultrafast palladium diffusion in germanium

    KAUST Repository

    Tahini, Hassan Ali

    2015-01-01

    The slow transport of dopants through crystal lattices has hindered the development of novel devices. Typically atoms are contained within deep potential energy wells which necessitates multiple attempts to hop between minimum energy positions. This is because the bonds that constrain atoms are strongest at the minimum positions. As they hop between sites the bonds must be broken, only to re-form as the atoms slide into adjacent minima. Here we demonstrate that the Pd atoms introduced into the Ge lattice behave differently. They retain bonds as the atoms shift across so that at the energy maximum between sites Pd still exhibits strong bonding characteristics. This reduces the energy maximum to almost nothing (a migration energy of only 0.03 eV) and means that the transport of Pd through the Ge lattice is ultrafast. We scrutinize the bonding characteristics at the atomic level using quantum mechanical simulation tools and demonstrate why Pd behaves so differently to other metals we investigated (i.e. Li, Cu, Ag, Pt and Au). Consequently, this fundamental understanding can be extended to systems where extremely rapid diffusion is desired, such as radiation sensors, batteries and solid oxide fuel cells.

  7. Diffusion Tensor Imaging of Pedophilia.

    Science.gov (United States)

    Cantor, James M; Lafaille, Sophie; Soh, Debra W; Moayedi, Massieh; Mikulis, David J; Girard, Todd A

    2015-11-01

    Pedophilia is a principal motivator of child molestation, incurring great emotional and financial burdens on victims and society. Even among pedophiles who never commit any offense,the condition requires lifelong suppression and control. Previous comparison using voxel-based morphometry (VBM)of MR images from a large sample of pedophiles and controls revealed group differences in white matter. The present study therefore sought to verify and characterize white matter involvement using diffusion tensor imaging (DTI), which better captures the microstructure of white matter than does VBM. Pedophilics ex offenders (n=24) were compared with healthy, age-matched controls with no criminal record and no indication of pedophilia (n=32). White matter microstructure was analyzed with Tract-Based Spatial Statistics, and the trajectories of implicated fiber bundles were identified by probabilistic tractography. Groups showed significant, highly focused differences in DTI parameters which related to participants’ genital responses to sexual depictions of children, but not to measures of psychopathy or to childhood histories of physical abuse, sexual abuse, or neglect. Some previously reported gray matter differences were suggested under highly liberal statistical conditions (p(uncorrected)pedophilia is characterized by neuroanatomical differences in white matter microstructure, over and above any neural characteristics attributable to psychopathy and childhood adversity, which show neuroanatomic footprints of their own. Although some gray matter structures were implicated previously, only few have emerged reliably.

  8. Simple simulation of diffusion bridges with application to likelihood inference for diffusions

    DEFF Research Database (Denmark)

    Bladt, Mogens; Sørensen, Michael

    2014-01-01

    With a view to statistical inference for discretely observed diffusion models, we propose simple methods of simulating diffusion bridges, approximately and exactly. Diffusion bridge simulation plays a fundamental role in likelihood and Bayesian inference for diffusion processes. First a simple...... the accuracy and efficiency of the approximate method and compare it to exact simulation methods. In the study, our method provides a very good approximation to the distribution of a diffusion bridge for bridges that are likely to occur in applications to statistical inference. To illustrate the usefulness...

  9. Treatment of chronic SFA in-stent occlusion with combined laser atherectomy and drug-eluting balloon angioplasty in patients with critical limb ischemia: a single-center, prospective, randomized study.

    Science.gov (United States)

    Gandini, Roberto; Del Giudice, Costantino; Merolla, Stefano; Morosetti, Daniele; Pampana, Enrico; Simonetti, Giovanni

    2013-12-01

    To compare the safety and efficacy of laser debulking (LD) and drug-eluting balloon (DEB) angioplasty to treatment with DEB angioplasty alone in patients affected by critical limb ischemia (CLI) and superficial femoral artery (SFA) chronic stent occlusion in a prospective, randomized study. Among 448 CLI patients treated from December 2009 to March 2011, 48 patients (39 men; mean age 72.7±7.8 years) with chronic SFA in-stent occlusion were randomly assigned to treatment using LD+DEB (n=24) or DEB angioplasty alone (n=24). Patency at 12 months was the primary outcome measure; secondary outcomes were target lesion revascularization (TLR) and clinical success at 12 months. In the LD+DEB group, the patency rates at 6 and 12 months (91.7% and 66.7%, respectively) were significantly higher (p=0.01) than in the DEB only patients (58.3% and 37.5%, respectively). TLR at 12 months was 16.7% in the LD+DEB group and 50% in the DEB only group (p=0.01). Two (8%) patients needed major amputations in the LD+DEB group vs. 11 (46%) in the DEB only group at 12 months (p=0.003). In this small initial experience, combined treatment with LD and DEB angioplasty is correlated with better outcomes in CLI patients with occluded SFA stents.

  10. Diffusion MRI and its Role in Neuropsychology.

    Science.gov (United States)

    Mueller, Bryon A; Lim, Kelvin O; Hemmy, Laura; Camchong, Jazmin

    2015-09-01

    Diffusion Magnetic Resonance Imaging (dMRI) is a popular method used by neuroscientists to uncover unique information about the structural connections within the brain. dMRI is a non-invasive imaging methodology in which image contrast is based on the diffusion of water molecules in tissue. While applicable to many tissues in the body, this review focuses exclusively on the use of dMRI to examine white matter in the brain. In this review, we begin with a definition of diffusion and how diffusion is measured with MRI. Next we introduce the diffusion tensor model, the predominant model used in dMRI. We then describe acquisition issues related to acquisition parameters and scanner hardware and software. Sources of artifacts are then discussed, followed by a brief review of analysis approaches. We provide an overview of the limitations of the traditional diffusion tensor model, and highlight several more sophisticated non-tensor models that better describe the complex architecture of the brain's white matter. We then touch on reliability and validity issues of diffusion measurements. Finally, we describe examples of ways in which dMRI has been applied to studies of brain disorders and how identified alterations relate to symptomatology and cognition.

  11. Diffusion of hydrogen fluoride in solid parahydrogen.

    Science.gov (United States)

    Ooe, Hiroki; Miyamoto, Yuki; Kuma, Susumu; Kawaguchi, Kentarou; Nakajima, Kyo; Nakano, Itsuo; Sasao, Noboru; Tang, Jian; Taniguchi, Takashi; Yoshimura, Motohiko

    2013-06-07

    We studied diffusion of hydrogen fluoride (HF) in solid parahydrogen (pH2) around 4 K. Diffusion rates were determined from time dependence of FT-IR spectra of HF monomers. The absorption of HF monomers shows temporal decay due to dimerization reaction via diffusion. It was found that the rates are affected by the sample temperature, the initial HF concentration, and annealing of samples. The observed non-Arrhenius-type temperature dependence suggests that the diffusion is dominated by a quantum tunneling process, that is, "quantum diffusion." Deceleration of the diffusion in condensed samples and acceleration in annealed samples were also observed. These results can be attributed to the fact that lower periodicity of samples due to impurities or defects suppresses the quantum tunneling. It seems to be difficult to explain the observed dependences by three possible diffusion mechanisms, exchange of chemical bonds, direct cyclic exchange, and exchange with mobile vacancy. Therefore, we propose a hypothetical mechanism by exchange of vacancies originating from quantum effect.

  12. Surface diffusion studies by optical diffraction techniques

    International Nuclear Information System (INIS)

    Xiao, X.D.

    1992-11-01

    The newly developed optical techniques have been combined with either second harmonic (SH) diffraction or linear diffraction off a monolayer adsorbate grating for surface diffusion measurement. Anisotropy of surface diffusion of CO on Ni(l10) was used as a demonstration for the second harmonic dim reaction method. The linear diffraction method, which possesses a much higher sensitivity than the SH diffraction method, was employed to study the effect of adsorbate-adsorbate interaction on CO diffusion on Ni(l10) surface. Results showed that only the short range direct CO-CO orbital overlapping interaction influences CO diffusion but not the long range dipole-dipole and CO-NI-CO interactions. Effects of impurities and defects on surface diffusion were further explored by using linear diffraction method on CO/Ni(110) system. It was found that a few percent S impurity can alter the CO diffusion barrier height to a much higher value through changing the Ni(110) surface. The point defects of Ni(l10) surface seem to speed up CO diffusion significantly. A mechanism with long jumps over multiple lattice distance initiated by CO filled vacancy is proposed to explain the observed defect effect

  13. Diffusion of bacteriophages through artificial biofilm models.

    Science.gov (United States)

    Hu, Jun; Miyanaga, Kazuhiko; Tanji, Yasunori

    2012-01-01

    The simple two-chamber diffusion method was improved to study the diffusion properties of bacteriophage (phage) T4 through a model biofilm agarose gel membrane (AGM) embedded with dead host Escherichia coli K12 cells. The apparent diffusion coefficient (D(app) ) of phage T4 was calculated to be 2.4 × 10(-12) m(2) /s in 0.5% AGM, which was lower than the coefficient of 4.2 × 10(-12) m(2) /s in 0.5% AGM without host cells. The phage adsorption process by dead host cells slowed the apparent phage diffusion. The Langmuir adsorption equation was used to simulate phage adsorption under different multiplicity of infections (MOIs); the maximum adsorbed phage MOI was calculated to be 417 PFU/CFU, and the Langmuir adsorption constant K(L) was 6.9 × 10(-4) CFU/PFU. To evaluate the effects of phage proliferation on diffusion, a simple syringe-based biofilm model was developed. The phage was added into this homogenous biofilm model when the host cells were in an exponential growth phase, and the apparent diffusion coefficient was greatly enhanced. We concluded that D(app) of phages through biofilms could be distinctly affected by phage adsorption and proliferation, and that the idea of D(app) and these methods can be used to study diffusion properties through real biofilms. Copyright © 2011 American Institute of Chemical Engineers (AIChE).

  14. Diffusion of insoluble carbon in zirconium oxides

    CERN Document Server

    Vykhodets, V B; Koester, U; Kondrat'ev, V V; Kesarev, A G; Hulsen, C; Kurennykh, T E

    2011-01-01

    The diffusion coefficient of insoluble carbon in zirconium oxides has been obtained for the temperature range of 900-1000A degrees C. There are no published data on the diffusion of insoluble impurities; these data are of current interest for the diffusion theory and nuclear technologies. Tracer atoms 13C have been introduced into oxides by means of ion implantation and the kinetics of their emission from the samples in the process of annealing in air has been analyzed. The measurements have been performed using the methods of nuclear microanalysis and X-ray photoelectron spectroscopy. The diffusion activation energy is 2.7 eV and the carbon diffusion coefficient is about six orders of magnitude smaller than that for oxygen self-diffusion in the same systems. This result indicates the strong anomaly of the diffusion properties of carbon in oxides. As a result, zirconium oxides cannot be used in some nuclear technologies, in particular, as a material of sources for accelerators of short-lived carbon isotopes.

  15. Emergent spatial synaptic structure from diffusive plasticity.

    Science.gov (United States)

    Sweeney, Yann; Clopath, Claudia

    2017-04-01

    Some neurotransmitters can diffuse freely across cell membranes, influencing neighbouring neurons regardless of their synaptic coupling. This provides a means of neural communication, alternative to synaptic transmission, which can influence the way in which neural networks process information. Here, we ask whether diffusive neurotransmission can also influence the structure of synaptic connectivity in a network undergoing plasticity. We propose a form of Hebbian synaptic plasticity which is mediated by a diffusive neurotransmitter. Whenever a synapse is modified at an individual neuron through our proposed mechanism, similar but smaller modifications occur in synapses connecting to neighbouring neurons. The effects of this diffusive plasticity are explored in networks of rate-based neurons. This leads to the emergence of spatial structure in the synaptic connectivity of the network. We show that this spatial structure can coexist with other forms of structure in the synaptic connectivity, such as with groups of strongly interconnected neurons that form in response to correlated external drive. Finally, we explore diffusive plasticity in a simple feedforward network model of receptive field development. We show that, as widely observed across sensory cortex, the preferred stimulus identity of neurons in our network become spatially correlated due to diffusion. Our proposed mechanism of diffusive plasticity provides an efficient mechanism for generating these spatial correlations in stimulus preference which can flexibly interact with other forms of synaptic organisation. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  16. Interests diffusion in social networks

    Science.gov (United States)

    D'Agostino, Gregorio; D'Antonio, Fulvio; De Nicola, Antonio; Tucci, Salvatore

    2015-10-01

    We provide a model for diffusion of interests in Social Networks (SNs). We demonstrate that the topology of the SN plays a crucial role in the dynamics of the individual interests. Understanding cultural phenomena on SNs and exploiting the implicit knowledge about their members is attracting the interest of different research communities both from the academic and the business side. The community of complexity science is devoting significant efforts to define laws, models, and theories, which, based on acquired knowledge, are able to predict future observations (e.g. success of a product). In the mean time, the semantic web community aims at engineering a new generation of advanced services by defining constructs, models and methods, adding a semantic layer to SNs. In this context, a leapfrog is expected to come from a hybrid approach merging the disciplines above. Along this line, this work focuses on the propagation of individual interests in social networks. The proposed framework consists of the following main components: a method to gather information about the members of the social networks; methods to perform some semantic analysis of the Domain of Interest; a procedure to infer members' interests; and an interests evolution theory to predict how the interests propagate in the network. As a result, one achieves an analytic tool to measure individual features, such as members' susceptibilities and authorities. Although the approach applies to any type of social network, here it is has been tested against the computer science research community. The DBLP (Digital Bibliography and Library Project) database has been elected as test-case since it provides the most comprehensive list of scientific production in this field.

  17. Stochastic models of technology diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Horner, S.M.

    1978-01-01

    Simple stochastic models of epidemics have often been employed by economists and sociologists in the study of the diffusion of information or new technology. In the present theoretical inquiry the properties of a family of models related to these epidemic processes are investigated, and use of the results in the study of technical change phenomena is demonstrated. A moving limit to the level of productivity of capital is hypothesized, the exact increment is determined exogenously by basic or applied research carried on outside the industry. It is this level of latent productivity (LPRO) which fills the role of the ''disease'' which ''spreads'' through the industry. In the single advance models, LPRO is assumed to have moved forward at some point in time, after which an individual firm may advance to the limit by virtue of its own research and development or through imitation of the successful efforts of another firm. In the recurrent advance models, LPRO is assumed to increase at either a constant absolute or relative rate. The firms, in the course of their research and imitation efforts, follow behind LPRO. Using the methods of stochastic processes, it is shown that these models are equivalent to ergodic Markov chains. Based on an assumption of constant intensity of R and D effort, it is shown how the single and recurrent advance models reflect on Joseph Schumpeter's hypothesis that more concentrated industries tend to be more technologically advanced than less concentrated. The results corroborate the weakest version of the hypothesis: monopoly prices need not be higher than competitive prices.

  18. Current limiting capability of diffused resistors

    International Nuclear Information System (INIS)

    Shedd, W.; Cappelli, J.

    1979-01-01

    An experimental evaluation of the current limiting capability of dielectrically isolated diffused resistors at transient ionizing dose rates up to 6*10 12 rads(Si)/sec is presented. Existing theoretical predictions of the transient response of diffused resistors are summarized and compared to the experimentally measured values. The test resistors used allow the effects of sheet resistance and geometry on the transient response to be determined. The experimental results show that typical dielectrically isolated diffused resistors maintain adequate current limiting capability for use in radiation hardened integrated circuits

  19. Phase space diffusion in turbulent plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans

    1990-01-01

    Turbulent diffusion of charged test particles in electrostatic plasma turbulence is reviewed. Two different types of test particles can be distinguished. First passive particles which are subject to the fluctuating electric fields without themselves contributing to the local space charge....... In terms of these test particle types, two basically different problems can be formulated. One deals with the diffusion of a particle with respect to its point of release in phase space. Alternatively the relative diffusion between many, or just two, particles can be analyzed. Analytical expressions...

  20. A tracer diffusion model derived from microstructure

    International Nuclear Information System (INIS)

    Lehikoinen, Jarmo; Muurinen, Arto; Olin, Markus

    2012-01-01

    Document available in extended abstract form only. Full text of publication follows: Numerous attempts have been made to explain the tracer diffusion of various solutes in compacted clays. These attempts have commonly suffered from an inability to describe the diffusion of uncharged and charged solutes with a single unified model. Here, an internally consistent approach to describing the diffusion of solutes in a heterogeneous porous medium, such as compacted bentonite, in terms of its microstructure is presented. The microstructure is taken to be represented by a succession of unit cells, which consist of two consecutive regions (Do, 1996). In the first region, the diffusion is viewed to occur in two parallel paths: one through microcrystalline units (micropores) and the other through meso-pores between the microcrystalline units. Solutes exiting these two paths are then joined together to continue diffusing through the second, disordered, region, connecting the two adjacent microcrystalline units. Adsorption (incl. co-ion exclusion) is thought to occur in the micropores, whereas meso-pores and the disordered region accommodate free species alone. Co-ions are also assumed to experience transfer resistance into and out of the micropores, which is characterized in the model by a transmission coefficient. Although the model is not new per se, its application to compacted clays has never been attempted before. It is shown that in the limit of strong adsorption, the effective diffusivity is limited from above only by the microstructural parameters of the model porous medium. As intuitive and logical as this result may appear, it has not been proven before. In the limit of vanishing disordered region, the effective diffusivity is no longer explicitly constrained by any of the model parameters. The tortuosity of the diffusion path, i.e. the quotient of the actual diffusion path length in the porous-medium coordinates and the characteristic length of the laboratory frame