The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Clemens Von Birgelen - One of the best experts on this subject based on the ideXlab platform.
-
scanning electron microscopic assessment of coating Irregularities and their precursors in unexpanded durable polymer based drug eluting stents
Catheterization and Cardiovascular Interventions, 2012Co-Authors: Mounir W Z Basalus, Kenneth Tandjung, Hanim Sen, Thea Van Westen, Dirk W Grijpma, Aart A Van Apeldoorn, Pasquelle K N Van Der Jagt, Clemens Von BirgelenAbstract:Objectives: To assess and quantify coating Irregularities on unexpanded and expanded durable polymer-based drug-eluting stents (DES) to gain insights into the origin of coating Irregularities. Background: Previous scanning electron microscopy (SEM) studies in various expanded DES revealed differences in frequency and size of coating Irregularities between DES types and specific distribution patterns, however, the origin of these Irregularities is unclear. Methods: We assessed at bench side a total of 1,200 SEM images obtained in 30 DES samples (15 expanded and 15 unexpanded) of Cypher Select Plus, Taxus Liberte, Endeavor, Xience V, and resolute. Results: For most coating Irregularities seen on expanded DES (72%; 23/32), a matching irregularity (n = 18/23) and/or its precursor (n = 11/23) was observed in unexpanded DES. Unexpanded Cypher select showed (small) crater lesions and cracks together with precursors of “peeling.” On unexpanded Taxus Liberte, thinning of polymer, small bare metal areas, wrinkles, and one precursor type were found. Unexpanded endeavor showed cracks, small bare metal areas, crater lesions, and precursors of the latter. Unexpanded Xience V and resolute mainly revealed crater lesions and their precursors. On unexpanded versus expanded DES, there was no difference in measured frequency of coating Irregularities and precursors (P = ns) with the exception of more bare metal areas on expanded Taxus Liberte (P = 0.01). Conclusions: Most coating Irregularities, or the potential to develop them, are inherent to the unexpanded DES. Important determinants of the formation of coating Irregularities may be the stent geometry and the physical properties of the coating, while stent-balloon interaction plays no major role.
-
tct 448 scanning electron microscopic observation of coating Irregularities and their precursors in unexpanded durable polymer based drug eluting stents
Journal of the American College of Cardiology, 2011Co-Authors: Mounir W Z Basalus, Kenneth Tandjung, Hanim Sen, Thea Van Westen, Dirk W Grijpma, Aart A Van Apeldoorn, Clemens Von BirgelenAbstract:Background: Previous scanning electron microscopy (SEM) studies in expanded DES revealed differences in the frequency and size of coating Irregularities between DES types and specific distribution patterns, however, the origin of these Irregularities is unclear.The current study quantifies coating Irregularities on unexpanded and expanded durable polymer-based drug-eluting stents (DES) to gain insights into the potential origin of coating Irregularities. Methods:We assessed at bench side a total of 1200 SEM images obtained in 30 DES samples (15 expanded and 15 unexpanded) of Cypher Select, Taxus Liberte, Endeavor, Xience V, and Resolute. Results: For most types of coating Irregularities seen on expanded DES (72%; 23/32), a matching irregularity (n=18/24) and/or its precursor (n=11/24) was observed in unexpanded corresponding DES. Only a few individual coating Irregularities (13%; 4/32) could not be accessed in unexpanded samples, as these Irregularities were located on the (invisible) luminal side. Unexpanded Cypher Select showed (small) crater lesions and cracks together with precursors of ‘peeling of polymer’. On unexpanded Taxus Liberte, thinning of polymer, small bare metal areas, wrinkles and one type of precursor was found. Unexpanded phosphorylcholine-based Endeavor stents showed cracks, small bare metal areas, and crater lesions as well as precursors of the latter. Unexpanded Xience V and Endeavor Resolute mainly revealed crater lesions and their precursors. Conclusion: SEM assessment demonstrated the presence of various coating Irregularities and/or their precursors on unexpanded durable polymer-based DES. These findings provide evidence that coating Irregularities arise during both DES manufacturing and stent expansion.
-
coating Irregularities of durable polymer based drug eluting stents as assessed by scanning electron microscopy
Eurointervention, 2009Co-Authors: Mounir W Z Basalus, Marc J K Ankone, Gert K Van Houwelingen, Frits H A F De Man, Clemens Von BirgelenAbstract:Aims: To classify and quantify post-expansion Irregularities in durable polymer-based coatings of drug-eluting stents (DES). Methods and results: Taxus Liberte™, Endeavor Sprint™, Endeavor Resolute™ and Xience V™ DES (three samples of each) were explored by light microscopy and scanning electron microscopy (SEM) following expansion at 14 atm in water. Incidence and size of Irregularities were measured during thorough quantitative examinations of a 360 SEM images. DES types examined showed a significant difference in the incidence of Irregularities (p<0.0001; 6.6±4.2/image at 60-fold magnification) with typical patterns specific for each DES. All types showed areas with bare metal-aspects, but incidence, shape, and size differed largely: Sprint showed the largest areas. Cracks were only found in Sprint and Resolute, while wrinkles were seen exclusively in Taxus Liberte and Xience V (p<0.0001). The coating of each DES type showed some inhomogeneity of distribution, but the incidence differed (p<0.0001) and was least in Taxus Liberte, which, on the other hand, was the only DES that showed webbing with large bare-metal exposure. Conclusions: The incidence and size of various coating Irregularities on different types of DES varied widely. These data may be considered in ongoing discussions on the differences between DES and may serve as reference to compare novel DES.
Mounir W Z Basalus - One of the best experts on this subject based on the ideXlab platform.
-
scanning electron microscopic assessment of coating Irregularities and their precursors in unexpanded durable polymer based drug eluting stents
Catheterization and Cardiovascular Interventions, 2012Co-Authors: Mounir W Z Basalus, Kenneth Tandjung, Hanim Sen, Thea Van Westen, Dirk W Grijpma, Aart A Van Apeldoorn, Pasquelle K N Van Der Jagt, Clemens Von BirgelenAbstract:Objectives: To assess and quantify coating Irregularities on unexpanded and expanded durable polymer-based drug-eluting stents (DES) to gain insights into the origin of coating Irregularities. Background: Previous scanning electron microscopy (SEM) studies in various expanded DES revealed differences in frequency and size of coating Irregularities between DES types and specific distribution patterns, however, the origin of these Irregularities is unclear. Methods: We assessed at bench side a total of 1,200 SEM images obtained in 30 DES samples (15 expanded and 15 unexpanded) of Cypher Select Plus, Taxus Liberte, Endeavor, Xience V, and resolute. Results: For most coating Irregularities seen on expanded DES (72%; 23/32), a matching irregularity (n = 18/23) and/or its precursor (n = 11/23) was observed in unexpanded DES. Unexpanded Cypher select showed (small) crater lesions and cracks together with precursors of “peeling.” On unexpanded Taxus Liberte, thinning of polymer, small bare metal areas, wrinkles, and one precursor type were found. Unexpanded endeavor showed cracks, small bare metal areas, crater lesions, and precursors of the latter. Unexpanded Xience V and resolute mainly revealed crater lesions and their precursors. On unexpanded versus expanded DES, there was no difference in measured frequency of coating Irregularities and precursors (P = ns) with the exception of more bare metal areas on expanded Taxus Liberte (P = 0.01). Conclusions: Most coating Irregularities, or the potential to develop them, are inherent to the unexpanded DES. Important determinants of the formation of coating Irregularities may be the stent geometry and the physical properties of the coating, while stent-balloon interaction plays no major role.
-
tct 448 scanning electron microscopic observation of coating Irregularities and their precursors in unexpanded durable polymer based drug eluting stents
Journal of the American College of Cardiology, 2011Co-Authors: Mounir W Z Basalus, Kenneth Tandjung, Hanim Sen, Thea Van Westen, Dirk W Grijpma, Aart A Van Apeldoorn, Clemens Von BirgelenAbstract:Background: Previous scanning electron microscopy (SEM) studies in expanded DES revealed differences in the frequency and size of coating Irregularities between DES types and specific distribution patterns, however, the origin of these Irregularities is unclear.The current study quantifies coating Irregularities on unexpanded and expanded durable polymer-based drug-eluting stents (DES) to gain insights into the potential origin of coating Irregularities. Methods:We assessed at bench side a total of 1200 SEM images obtained in 30 DES samples (15 expanded and 15 unexpanded) of Cypher Select, Taxus Liberte, Endeavor, Xience V, and Resolute. Results: For most types of coating Irregularities seen on expanded DES (72%; 23/32), a matching irregularity (n=18/24) and/or its precursor (n=11/24) was observed in unexpanded corresponding DES. Only a few individual coating Irregularities (13%; 4/32) could not be accessed in unexpanded samples, as these Irregularities were located on the (invisible) luminal side. Unexpanded Cypher Select showed (small) crater lesions and cracks together with precursors of ‘peeling of polymer’. On unexpanded Taxus Liberte, thinning of polymer, small bare metal areas, wrinkles and one type of precursor was found. Unexpanded phosphorylcholine-based Endeavor stents showed cracks, small bare metal areas, and crater lesions as well as precursors of the latter. Unexpanded Xience V and Endeavor Resolute mainly revealed crater lesions and their precursors. Conclusion: SEM assessment demonstrated the presence of various coating Irregularities and/or their precursors on unexpanded durable polymer-based DES. These findings provide evidence that coating Irregularities arise during both DES manufacturing and stent expansion.
-
coating Irregularities of durable polymer based drug eluting stents as assessed by scanning electron microscopy
Eurointervention, 2009Co-Authors: Mounir W Z Basalus, Marc J K Ankone, Gert K Van Houwelingen, Frits H A F De Man, Clemens Von BirgelenAbstract:Aims: To classify and quantify post-expansion Irregularities in durable polymer-based coatings of drug-eluting stents (DES). Methods and results: Taxus Liberte™, Endeavor Sprint™, Endeavor Resolute™ and Xience V™ DES (three samples of each) were explored by light microscopy and scanning electron microscopy (SEM) following expansion at 14 atm in water. Incidence and size of Irregularities were measured during thorough quantitative examinations of a 360 SEM images. DES types examined showed a significant difference in the incidence of Irregularities (p<0.0001; 6.6±4.2/image at 60-fold magnification) with typical patterns specific for each DES. All types showed areas with bare metal-aspects, but incidence, shape, and size differed largely: Sprint showed the largest areas. Cracks were only found in Sprint and Resolute, while wrinkles were seen exclusively in Taxus Liberte and Xience V (p<0.0001). The coating of each DES type showed some inhomogeneity of distribution, but the incidence differed (p<0.0001) and was least in Taxus Liberte, which, on the other hand, was the only DES that showed webbing with large bare-metal exposure. Conclusions: The incidence and size of various coating Irregularities on different types of DES varied widely. These data may be considered in ongoing discussions on the differences between DES and may serve as reference to compare novel DES.
Jorge L Chau - One of the best experts on this subject based on the ideXlab platform.
-
gravity wave induced ionospheric Irregularities in the postsunset equatorial valley region
Journal of Geophysical Research, 2017Co-Authors: D L Hysell, David C Fritts, Brian Laughman, Jorge L ChauAbstract:Plasma Irregularities in the postsunset equatorial valley region ionosphere are investigated experimentally and through numerical simulation. Coherent radar backscatter observed at the Jicamarca Radio Observatory shows two classes of Irregularities in different altitude bands – one mainly below about 125 km and the other mainly above. Irregularities in both bands are organized into wavefronts with wavelengths of a few km. However, only the Irregularities in the high-altitude band exhibit consistent propagation speeds and directions. Some previous observations of Irregularities in the nighttime electrojet suggest that gravity waves may sometimes influence their morphology. The possibility that the valley-region Irregularities are also related to gravity waves (GWs) is therefore investigated numerically. A model of a GW packet propagating through a tidal wind field is used to drive another model which predicts the resulting ionospheric electrodynamics. The combined simulation shows that GWs can induce field-aligned currrents and excite resistive drift waves which could be responsible for the valley-region Irregularities in the high-altitude band. The GWs also induce Irregularities in the upper E region directly through simple dynamo action which subsequently deform under the influence of shear flow. This may explain the Irregularities in the low-altitude band.
-
gravity wave induced ionospheric Irregularities in the postsunset equatorial valley region
Journal of Geophysical Research, 2017Co-Authors: D L Hysell, David C Fritts, Brian Laughman, Jorge L ChauAbstract:Plasma Irregularities in the postsunset equatorial valley region ionosphere are investigated experimentally and through numerical simulation. Coherent radar backscatter observed at the Jicamarca Radio Observatory shows two classes of Irregularities in different altitude bands – one mainly below about 125 km and the other mainly above. Irregularities in both bands are organized into wavefronts with wavelengths of a few km. However, only the Irregularities in the high-altitude band exhibit consistent propagation speeds and directions. Some previous observations of Irregularities in the nighttime electrojet suggest that gravity waves may sometimes influence their morphology. The possibility that the valley-region Irregularities are also related to gravity waves (GWs) is therefore investigated numerically. A model of a GW packet propagating through a tidal wind field is used to drive another model which predicts the resulting ionospheric electrodynamics. The combined simulation shows that GWs can induce field-aligned currrents and excite resistive drift waves which could be responsible for the valley-region Irregularities in the high-altitude band. The GWs also induce Irregularities in the upper E region directly through simple dynamo action which subsequently deform under the influence of shear flow. This may explain the Irregularities in the low-altitude band.
D L Hysell - One of the best experts on this subject based on the ideXlab platform.
-
gravity wave induced ionospheric Irregularities in the postsunset equatorial valley region
Journal of Geophysical Research, 2017Co-Authors: D L Hysell, David C Fritts, Brian Laughman, Jorge L ChauAbstract:Plasma Irregularities in the postsunset equatorial valley region ionosphere are investigated experimentally and through numerical simulation. Coherent radar backscatter observed at the Jicamarca Radio Observatory shows two classes of Irregularities in different altitude bands – one mainly below about 125 km and the other mainly above. Irregularities in both bands are organized into wavefronts with wavelengths of a few km. However, only the Irregularities in the high-altitude band exhibit consistent propagation speeds and directions. Some previous observations of Irregularities in the nighttime electrojet suggest that gravity waves may sometimes influence their morphology. The possibility that the valley-region Irregularities are also related to gravity waves (GWs) is therefore investigated numerically. A model of a GW packet propagating through a tidal wind field is used to drive another model which predicts the resulting ionospheric electrodynamics. The combined simulation shows that GWs can induce field-aligned currrents and excite resistive drift waves which could be responsible for the valley-region Irregularities in the high-altitude band. The GWs also induce Irregularities in the upper E region directly through simple dynamo action which subsequently deform under the influence of shear flow. This may explain the Irregularities in the low-altitude band.
-
gravity wave induced ionospheric Irregularities in the postsunset equatorial valley region
Journal of Geophysical Research, 2017Co-Authors: D L Hysell, David C Fritts, Brian Laughman, Jorge L ChauAbstract:Plasma Irregularities in the postsunset equatorial valley region ionosphere are investigated experimentally and through numerical simulation. Coherent radar backscatter observed at the Jicamarca Radio Observatory shows two classes of Irregularities in different altitude bands – one mainly below about 125 km and the other mainly above. Irregularities in both bands are organized into wavefronts with wavelengths of a few km. However, only the Irregularities in the high-altitude band exhibit consistent propagation speeds and directions. Some previous observations of Irregularities in the nighttime electrojet suggest that gravity waves may sometimes influence their morphology. The possibility that the valley-region Irregularities are also related to gravity waves (GWs) is therefore investigated numerically. A model of a GW packet propagating through a tidal wind field is used to drive another model which predicts the resulting ionospheric electrodynamics. The combined simulation shows that GWs can induce field-aligned currrents and excite resistive drift waves which could be responsible for the valley-region Irregularities in the high-altitude band. The GWs also induce Irregularities in the upper E region directly through simple dynamo action which subsequently deform under the influence of shear flow. This may explain the Irregularities in the low-altitude band.
-
an overview and synthesis of plasma Irregularities in equatorial spread f
Journal of Atmospheric and Solar-Terrestrial Physics, 2000Co-Authors: D L HysellAbstract:Abstract A unified picture of plasma Irregularities in equatorial spread F is developed from the analysis of satellite, sounding rocket, and coherent scatter radar observations. The coherent scatter data are analyzed using a new in-beam radar imaging technique that permits direct comparison between radar data, in situ data, and computer simulations of the Irregularities. Three varieties of Irregularities, all produced by ionospheric interchange instabilities, are found to occur. Thin bottom-type layers are composed of waves with primary transverse wavelengths less than about 1 km and with significant parallel wavenumbers. These exist on magnetic flux tubes controlled by the E region dynamo and drift westward in the postsunset ionosphere. A nonlocal analysis is used to calculate their linear growth rate. When the F region dynamo takes control of the flux tube, bottomside Irregularities can emerge. These are more robust Irregularities with longer primary wavelengths and which exhibit greater vertical development. Nonlinear analyses explain the appearance of steepened structures in rocket observations and solitary waves in satellite observations of bottomside layers. The one-dimensional spectra of these Irregularities obey power laws but are anisotropic and have variable spectral indices and spectral breaks. Very strong polarization electric fields can eject large regions of deeply depleted plasma through the F peak and form topside Irregularities. Theoretical calculations supported by satellite data show that ion inertia may become important for topside Irregularities. The one-dimensional spectra of Irregularities in the inertial regime obey a k −5/3 power law, but strong plasma inhomogeneity implies that Kolmogorov weak turbulence is not the explanation. Topside depletions are shown to bifurcate and also to pinch off from the bottomside.
Thea Van Westen - One of the best experts on this subject based on the ideXlab platform.
-
scanning electron microscopic assessment of coating Irregularities and their precursors in unexpanded durable polymer based drug eluting stents
Catheterization and Cardiovascular Interventions, 2012Co-Authors: Mounir W Z Basalus, Kenneth Tandjung, Hanim Sen, Thea Van Westen, Dirk W Grijpma, Aart A Van Apeldoorn, Pasquelle K N Van Der Jagt, Clemens Von BirgelenAbstract:Objectives: To assess and quantify coating Irregularities on unexpanded and expanded durable polymer-based drug-eluting stents (DES) to gain insights into the origin of coating Irregularities. Background: Previous scanning electron microscopy (SEM) studies in various expanded DES revealed differences in frequency and size of coating Irregularities between DES types and specific distribution patterns, however, the origin of these Irregularities is unclear. Methods: We assessed at bench side a total of 1,200 SEM images obtained in 30 DES samples (15 expanded and 15 unexpanded) of Cypher Select Plus, Taxus Liberte, Endeavor, Xience V, and resolute. Results: For most coating Irregularities seen on expanded DES (72%; 23/32), a matching irregularity (n = 18/23) and/or its precursor (n = 11/23) was observed in unexpanded DES. Unexpanded Cypher select showed (small) crater lesions and cracks together with precursors of “peeling.” On unexpanded Taxus Liberte, thinning of polymer, small bare metal areas, wrinkles, and one precursor type were found. Unexpanded endeavor showed cracks, small bare metal areas, crater lesions, and precursors of the latter. Unexpanded Xience V and resolute mainly revealed crater lesions and their precursors. On unexpanded versus expanded DES, there was no difference in measured frequency of coating Irregularities and precursors (P = ns) with the exception of more bare metal areas on expanded Taxus Liberte (P = 0.01). Conclusions: Most coating Irregularities, or the potential to develop them, are inherent to the unexpanded DES. Important determinants of the formation of coating Irregularities may be the stent geometry and the physical properties of the coating, while stent-balloon interaction plays no major role.
-
tct 448 scanning electron microscopic observation of coating Irregularities and their precursors in unexpanded durable polymer based drug eluting stents
Journal of the American College of Cardiology, 2011Co-Authors: Mounir W Z Basalus, Kenneth Tandjung, Hanim Sen, Thea Van Westen, Dirk W Grijpma, Aart A Van Apeldoorn, Clemens Von BirgelenAbstract:Background: Previous scanning electron microscopy (SEM) studies in expanded DES revealed differences in the frequency and size of coating Irregularities between DES types and specific distribution patterns, however, the origin of these Irregularities is unclear.The current study quantifies coating Irregularities on unexpanded and expanded durable polymer-based drug-eluting stents (DES) to gain insights into the potential origin of coating Irregularities. Methods:We assessed at bench side a total of 1200 SEM images obtained in 30 DES samples (15 expanded and 15 unexpanded) of Cypher Select, Taxus Liberte, Endeavor, Xience V, and Resolute. Results: For most types of coating Irregularities seen on expanded DES (72%; 23/32), a matching irregularity (n=18/24) and/or its precursor (n=11/24) was observed in unexpanded corresponding DES. Only a few individual coating Irregularities (13%; 4/32) could not be accessed in unexpanded samples, as these Irregularities were located on the (invisible) luminal side. Unexpanded Cypher Select showed (small) crater lesions and cracks together with precursors of ‘peeling of polymer’. On unexpanded Taxus Liberte, thinning of polymer, small bare metal areas, wrinkles and one type of precursor was found. Unexpanded phosphorylcholine-based Endeavor stents showed cracks, small bare metal areas, and crater lesions as well as precursors of the latter. Unexpanded Xience V and Endeavor Resolute mainly revealed crater lesions and their precursors. Conclusion: SEM assessment demonstrated the presence of various coating Irregularities and/or their precursors on unexpanded durable polymer-based DES. These findings provide evidence that coating Irregularities arise during both DES manufacturing and stent expansion.
