scholarly journals A mechanistic analysis of delamination of elastic coatings from the surface of plastically deformed stents

2020 ◽  
Author(s):  
Eamon Ó Máirtín ◽  
Jamie Concannon ◽  
Guillaume Parry ◽  
Patrick McGarry
Keyword(s):  
Polymer Coatings ◽  
Adverse Outcomes ◽  
Design Parameters ◽  
Stent Deployment ◽  
Reliable Assessment ◽  
Hardening Modulus ◽  
Coating Delamination ◽  
Low Levels ◽  
High Level ◽  
Stent Coating

Several medical papers have reported delamination of the coating from the stent-substrate following intravascular deployment leading to adverse outcomes for patients. However, the mechanisms of delamination of such polymer coatings from the surface of a stent due to large deformations during device deployment has not been studied. In this paper, a novel and in-depth investigation of the mechanisms and parameters that govern stent-coating delamination is performed, using a cohesive zone formulation to simulation the evolution of traction at the stent-coating interface. The study firstly analyses the behaviour of elastic coatings on idealised elastic stent substrates. Simulations reveal that the mode mixity of delamination is strongly dependent on the level of stent deployment at initiation. In general, peak normal tractions exceed peak shear tractions at low levels of stent deployment whereas the reverse trend is computed at high levels of stent deployment. Interface tractions increase with both increasing stent thickness and coating thickness suggesting that thinner stents and thinner coatings should be utilised for the delivery of antiproliferative drugs in order to reduce the risk of coating delamination. Next, the influence of stent plasticity on interface tractions and coating delamination is investigated. Even at low levels of deployment, plastic yielding occurs in the stent hinge region and the patterns of normal and shear tractions are found to be significantly more complex than those computed for elastic stents, with both tensile and compressive regions of normal traction occurring in the stent arch. At a high level of stent deployment shear tractions at the stent-coating interface are computed to increase with decreasing strain hardening modulus. The findings of this paper provide a new insight into the stress-state at the stent-coating interface as a function of the stent design parameters and large deformation elasticity and plasticity during deployment, allowing for a more reliable assessment of the limits relating to safe implantation of coated stents.

Computer Modeling of Cardiovascular Stent Coating Damage

2008 ◽  
Author(s):  
Caroline G. Hopkins ◽  
Peter E. McHugh ◽  
J. Patrick McGarry
Keyword(s):  
Finite Element ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Polymer Coatings ◽  
Zone Model ◽  
Computational Simulations ◽  
Cardiovascular Stent ◽  
Coating Delamination ◽  
Stent Coating ◽  
Stent Surface

In this paper computational simulations of stent coating debonding are presented. Finite element methods are implemented to model coating delamination during stent crimping, deployment and recoil. Gold, titanium and polymer coatings of differing thicknesses are explicitly modeled. The interfacial relationship between the stent surface and the coating during crimping and deployment is simulated using a cohesive zone model.

High world sugar prices: is Asia’s production cycle to blame?

2010 ◽  
pp. 169-173
Author(s):  
Martin Todd
Keyword(s):  
Supply Chain ◽  
Supply And Demand ◽  
Production Cycle ◽  
Low Levels ◽  
High Level ◽  
High World

The current high world sugar prices reflect a major imbalance between global supply and demand, which has reduced stocks to very low levels. Although it remains to be seen whether prices will rise much above current values, it is clear that the supply chain will remain stretched throughout 2010 and this will help to maintain prices at a high level.

Lower perception of pharmacological treatment increases risk of non-adherence to medication

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
CB Graversen ◽  
JB Valentin ◽  
ML Larsen ◽  
S Riahi ◽  
T Holmberg ◽  
...  
Keyword(s):  
Pharmacological Treatment ◽  
Poisson Regression ◽  
Drug Class ◽  
Angiotensin Receptor Blockers ◽  
Adverse Outcomes ◽  
Adherence To Medication ◽  
Increased Risk ◽  
Patient Reported ◽  
High Level

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): The Danish Heart Foundation Background A large proportion of patients fail to reach optimal adherence to medication following incident ischemic heart disease (IHD) despite amble evidence of the beneficial effect of medication. Non-adherence to medication increases risk of disease-related adverse outcomes but none has explored how perception about pharmacological treatment detail on non-adherence using register-based follow-up data. Purpose To investigate the association between patients’ perception of pharmacological treatment and risk of non-initiation and non-adherence to medication in a population with incident IHD. Methods This cohort study followed 871 patients until 365 days after incident IHD. The study combined patient-reported survey data on perception about pharmacological treatment (categorised by ‘To a high level’, ‘To some level’, and ‘To a lesser level’) with register-based data on reimbursed prescription of cardiovascular medication (antithrombotics, statins, ACE-inhibitors/angiotensin receptor blockers, and β-blockers). Non-initiation was defined as no pick-up of medication in the first 180 days following incident IHD and analysed by Poisson regression. Two different measures evaluated non-adherence in patients initiating treatment: 1) proportion of days covered (PDC) analysed by Poisson regression, and 2) risk of discontinuation analysed by Cox proportional hazard regression. All analyses were adjusted for confounding variables (age, sex, ethnicity, income, educational level, civil status, occupation, charlson comorbidity index, supportive relatives, and individual consultation in medication) identified by directed acyclic graph and obtained from national registers and the survey. Item non-response was handled by multiple imputation and item consistency was evaluated by McDonalds omega. Results Lower perceptions about pharmacological treatment was associated with increased risk of non-initiation and non-adherence to medication irrespectively of drug class and adherence measure in the multiple adjusted analyses (please see figure illustrating results on antithrombotics). A dose-response relationship was observed both at 180- and 365-days of follow-up, but the steepest decline in adherence differed when comparing the two adherence measures (results not shown). Moderate internal consistency was found for the summed measure of perception (McDonalds omega = 0.67). Conclusion Lower perception of pharmacological treatment was associated with subsequent non-initiation and non-adherence to medication, irrespectively of measurement method and drug class. Abstract Figure. Figre: Multiple adjusted analyses

Making Up 3D Bodies

2021 ◽  
Vol 4 (2) ◽  
pp. 1-9
Author(s):  
Kiona Hagen Niehaus ◽  
Rebecca Fiebrink
Keyword(s):  
Software Tool ◽  
The Body ◽  
Design Parameters ◽  
Artistic Practice ◽  
Human Form ◽  
Modeling Systems ◽  
Exploratory Approach ◽  
Disability Status ◽  
High Level ◽  
The Impact

This paper describes the process of developing a software tool for digital artistic exploration of 3D human figures. Previously available software for modeling mesh-based 3D human figures restricts user output based on normative assumptions about the form that a body might take, particularly in terms of gender, race, and disability status, which are reinforced by ubiquitous use of range-limited sliders mapped to singular high-level design parameters. CreatorCustom, the software prototype created during this research, is designed to foreground an exploratory approach to modeling 3D human bodies, treating the digital body as a sculptural landscape rather than a presupposed form for rote technical representation. Building on prior research into serendipity in Human-Computer Interaction and 3D modeling systems for users at various levels of proficiency, among other areas, this research comprises two qualitative studies and investigation of the impact on the first author's artistic practice. Study 1 uses interviews and practice sessions to explore the practices of six queer artists working with the body and the language, materials, and actions they use in their practice; these then informed the design of the software tool. Study 2 investigates the usability, creativity support, and bodily implications of the software when used by thirteen artists in a workshop. These studies reveal the importance of exploration and unexpectedness in artistic practice, and a desire for experimental digital approaches to the human form.

scholarly journals Evaluation of Static Mapping for Dynamic Space-Shared Multi-task Processing on FPGAs

2021 ◽  
Author(s):  
Umar Ibrahim Minhas ◽  
Roger Woods ◽  
Georgios Karakonstantis
Keyword(s):  
High Performance ◽  
Design Space Exploration ◽  
Design Space ◽  
System Throughput ◽  
Design Parameters ◽  
Temporal Constraints ◽  
Shared Resources ◽  
Task Processing ◽  
High Level ◽  
Performance Computing

AbstractWhilst FPGAs have been used in cloud ecosystems, it is still extremely challenging to achieve high compute density when mapping heterogeneous multi-tasks on shared resources at runtime. This work addresses this by treating the FPGA resource as a service and employing multi-task processing at the high level, design space exploration and static off-line partitioning in order to allow more efficient mapping of heterogeneous tasks onto the FPGA. In addition, a new, comprehensive runtime functional simulator is used to evaluate the effect of various spatial and temporal constraints on both the existing and new approaches when varying system design parameters. A comprehensive suite of real high performance computing tasks was implemented on a Nallatech 385 FPGA card and show that our approach can provide on average 2.9 × and 2.3 × higher system throughput for compute and mixed intensity tasks, while 0.2 × lower for memory intensive tasks due to external memory access latency and bandwidth limitations. The work has been extended by introducing a novel scheduling scheme to enhance temporal utilization of resources when using the proposed approach. Additional results for large queues of mixed intensity tasks (compute and memory) show that the proposed partitioning and scheduling approach can provide higher than 3 × system speedup over previous schemes.

scholarly journals Testing Todd: family types and development

2021 ◽  
pp. 1-18
Author(s):  
Jerg Gutmann ◽  
Stefan Voigt
Keyword(s):  
Rule Of Law ◽  
Civil Society Organizations ◽  
The Rule Of Law ◽  
State Fragility ◽  
Family Types ◽  
Low Levels ◽  
Parsimonious Model ◽  
The One ◽  
High Level

Abstract Many years ago, Emmanuel Todd came up with a classification of family types and argued that the historically prevalent family types in a society have important consequences for its economic, political, and social development. Here, we evaluate Todd's most important predictions empirically. Relying on a parsimonious model with exogenous covariates, we find mixed results. On the one hand, authoritarian family types are, in stark contrast to Todd's predictions, associated with increased levels of the rule of law and innovation. On the other hand, and in line with Todd's expectations, communitarian family types are linked to racism, low levels of the rule of law, and late industrialization. Countries in which endogamy is frequently practiced also display an expectedly high level of state fragility and weak civil society organizations.

Flavonoids and UV Photoprotection in Arabidopsis Mutants

2001 ◽  
Vol 56 (9-10) ◽  
pp. 745-754 ◽  
Author(s):  
Ken G Ryan ◽  
Ewald E Swinny ◽  
Chris Winefield ◽  
Kenneth R Markham
Keyword(s):  
Crucial Role ◽  
Hydroxycinnamic Acid ◽  
Ultraviolet B ◽  
Uvb Radiation ◽  
Wild Type ◽  
Hydroxycinnamic Acid Derivatives ◽  
Quercetin Glycosides ◽  
Kaempferol Glycosides ◽  
Low Levels ◽  
High Level

AbstractWild-type Arabidopsis L. leaves exposed to low ultraviolet-B (U V B ) conditions contained predominantly kaempferol glycosides, with low levels of quercetin glycosides. The flavonoid level doubled on treatment with UVB and an increase in the ratio of quercetin: kaempferol was observed. These results suggest that flavonols protect Arabidopsis plants from UVB damage, and indicate that the flavonoid 3’-hydroxylase (F3’H) enzyme, which converts dihydrokaempferol to dihydroquercetin, may play a crucial role. The tt7 mutant lacks this gene and, after treatment with sub-ambient UVB, contained kaempferol glycosides exclusively, to a level of total flavonols similar to that in wild-type Arabidopsis. Total flavonols after enhanced UVB treatment were higher in tt7 than in similarly treated wild-type plants, and only kaempferol glycosides were detected. Despite this high level, tt7 plants were less tolerant of UVB radiation than wild-type plants. These observations suggests that kaempferol is a less effective photoprotectant than quercetin. The chalcone isomerase (CHI) mutant (tt5) surprisingly did not accumulate naringenin chalcone, and this suggests that the mutation may not be restricted to the CHI gene alone. The concentration of hydroxycinnamic acid derivatives did not change with UVB treatment in most varieties indicating that their role in UV photoprotection may be subordinate to that of the flavonoids.

The dynamics of Holocene monsoon based on meteoric 10Be at Kunlun Pass on the northeastern Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Peng Chen ◽  
Zhongbo Yu ◽  
Markus Czymzik ◽  
Ala Aldahan ◽  
Jinguo Wang ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Early Holocene ◽  
Tibet Plateau ◽  
The Holocene ◽  
Proxy Records ◽  
Low Levels ◽  
High Level ◽  
Qinghai Tibet Plateau

<p>Multiple proxy records have been used for the understanding of environmental and climate changes during the Holocene. For the first time, we here measure meteoric <sup>10</sup>Be isotope of sediments from a drill core collected at the Kunlun Pass (KP) on the northeastern Qinghai-Tibet Plateau (NETP) to investigate mositure and atmospheric circulation changes during the Holocene. The <sup>10</sup>Be flux suggests relative low levels in the Early Holocene, followed by a sharp increase to high values at around 4 ka BP (4 ka BP = 4000 years before present). Afterwards, the <sup>10</sup>Be flux remains on a high level during the Late Holocene, but decreases slightly towards today. These <sup>10</sup>Be deposition patterns are compared to moisture changes in regions dominated by the Indian Summer Monsoon (ISM), East Asian Summer Monsoon (EASM), and the Westerlies. Different from the gradual changes in monsoon patterns, the <sup>10</sup>Be data reveal low levels during the Early Holocene until ~4 ka BP when an obvious increase was indicated and a relative high level continues to this day, which is relatively more in agreement with patterns of the Westerlies. This finding provides a new evidence for a shift in the dominant pattern of atmospheric circulation at the KP region from a more monsoonal one to one dominated by the Westerlies. Our results improve the understanding of non-stationary interactions and spatial relevance of the EASM, the ISM and the Westerlies on the Qinghai-Tibet Plateau.</p>

scholarly journals An analysis of urban renewal decision-making in China from the perspective of transaction costs theory: the case of Chongqing

2020 ◽  
Vol 35 (4) ◽  
pp. 1177-1199
Author(s):  
Taozhi Zhuang ◽  
Queena K. Qian ◽  
Henk J. Visscher ◽  
Marja G. Elsinga
Keyword(s):  
Decision Making ◽  
Transaction Costs ◽  
Urban Renewal ◽  
Municipal Government ◽  
Analytical Framework ◽  
Adverse Outcomes ◽  
Policy Implications ◽  
Stakeholder Groups ◽  
High Level ◽  
The Empirical Analysis

Abstract In China, there is a growing number of urban renewal projects due to the rapid growth of the economy and urbanization. To meet the needs of urban development, urban renewal requires a sound decision-making approach involving various stakeholder groups. However, current urban renewal decision-making is criticized for poor efficiency, equity, and resulting in many unintended adverse outcomes. It is claimed that high-level transaction costs (e.g., a great deal of time spent on negotiation and coordination) are the factors hidden behind the problems. However, few studies have analyzed urban renewal decision-making in a transaction costs perspective. Using the case of Chongqing, this paper aims at adopting transaction costs theory to understand the administrative process of urban renewal decision-making in China. This research focuses on four key stakeholder groups: municipal government, district government, local administrative organizations, and the consulting parties. A transaction costs analytical framework is established. First, the decision-making stages of urban renewal and involved key stakeholder groups are clarified. Second, the transactions done by different stakeholder groups in each stage is identified, thus to analyze what types of transaction costs are generated. Third, the relative levels of transaction costs among different stakeholder groups were measured based on the interview. The empirical analysis reveals how transaction costs occur and affect urban renewal decision-making. Finally, policy implications were proposed to reduce transaction costs in order to enhance urban renewal.

scholarly journals The Effect of Problem Based Learning Models and Levels of Creativity Toward Student Outcomes in Vocational High School

2019 ◽  
Vol 1 (6) ◽  
Author(s):  
Dasining Dasining ◽  
Supari Muslim ◽  
Sri Handajani
Keyword(s):  
Student Learning ◽  
Learning Outcomes ◽  
Problem Based Learning ◽  
Student Learning Outcomes ◽  
Learning Model ◽  
Higher Learning ◽  
Learning Models ◽  
Low Levels ◽  
Direct Learning ◽  
High Level

This study aims to determine the level of creativity of students who are taught using problem based learning models and students who are taught using direct learning models. To find out the learning outcomes of students who have a high level of creativity and creativity level of creativity is low. The method used in this study is Quasi Experimental. The design used is a 2x2 factorial design, because this design can be used to see student learning outcomes before administering treatments and after giving treatments. The results of the study found: (1) the level of creativity of students who study using a learning model based on higher learning outcomes compared to students who learn with the direct learning model; (2) student learning outcomes with a high level of creativity, significantly higher than students who have low levels of creativity; and (3) there is an interaction between the use of learning models and the level of creativity on student learning outcomes. This study concludes that: (1) problem based learning models can improve student creativity; (2) students who have a high level of creativity, higher learning outcomes than students who have low levels of creativity; and (3) there is an interaction between the use of learning models and the level of creativity on student learning outcomes.

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