scholarly journals Numerical Simulation of LVAD Inflow Cannulas with Different Tip

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Guang-Mao Liu ◽  
Hai-Bo Chen ◽  
Fu-Liang Luo ◽  
Yan Zhang ◽  
Han-Song Sun ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Left Ventricle ◽  
Blood Compatibility ◽  
Flow Behavior ◽  
Low Velocity ◽  
Smooth Flow ◽  
Velocity Flow ◽  
Inflow Cannula ◽  
Major Factors

The tip structure of LVAD inflow cannula is one of major factors to lead adverse events such as thrombosis and suction leading to obstruction. In this research, four kinds of tips that had been used in inflow cannulas were selected and designed. The flow field of the four inflow cannulas inserted into the apex of left ventricle (LV) was numerically computed by computational fluid dynamics. The flow behavior was analyzed in order to compare the blood compatibility and suction in left ventricle and cannulas after the inflow cannulas with different tips were inserted to the apex of LV. The results showed that the cannula tip structure affected the LVAD performance. Among these four cannulas, the trumpet-tipped inflow cannula owned the best performance in smooth flow velocity distribution without backflow or low-velocity flow so that it was the best in blood compatibility. Nevertheless, the caged tipped cannula was the worst in blood compatibility. And the blunt-tipped and beveled tipped inflow cannulas may obstruct more easily than trumpet and caged tipped inflow cannulas because of their shape. The study indicated that the trumpet tip was the most preferable for the inflow cannula of long-term LVAD.

scholarly journals Numerical analysis of the effect of the design of axial-flow pump cannula tip on stagnation and recirculation zones in the left ventricle

2020 ◽  
Vol 22 (2) ◽  
pp. 107-112
Author(s):  
M. S. Nosov ◽  
G. P. Itkin ◽  
V. M. Zaiko ◽  
V. A. Malgichev
Keyword(s):  
Left Ventricle ◽  
Axial Flow ◽  
Left Ventricular ◽  
Ventricular Assist ◽  
Axial Flow Blood Pump ◽  
Left Ventricular Assist ◽  
Inflow Cannula ◽  
Recirculation Zones ◽  
Axial Flow Pump

Objective: to analyze the inflow cannula of an implantable axial-flow blood pump for a long-term left ventricular assist system in order to minimize thromboembolic complications. Materials and methods. Hemodynamics was considered for 4 different designs of the inflow cannula, from 0 mm to 25 mm long. Areas at the base of the cannula received the most attention. Analysis was performed using the OpenFOAM software. Results. It was revealed that sizes of stagnation and recirculation zones directly depended on the length of the cannula when placed in the left ventricle. Accordingly, longer cannula increases the risk of thrombosis. Conclusion. The design of an inflow cannula determines the likelihood of thrombosis in the cannula. Longer inflow cannula increases stagnation and recirculation zones. This provides a basis for a search for other possible modifications.

609 Noninvasive left ventricle contractility assessment in patients with long-term volume overload

1999 ◽  
Vol 1 ◽  
pp. S101-S101
Author(s):  
O FOKINA ◽  
N TVERDOKHLEBOV ◽  
V SANDRIKOV ◽  
L KOUZNETZOVA
Keyword(s):  
Left Ventricle ◽  
Volume Overload

scholarly journals Satellite-Derived Protein Concentration of Phytoplankton in the Southwestern East/Japan Sea

2021 ◽  
Vol 9 (2) ◽  
pp. 189
Author(s):  
Hyeonji Bae ◽  
Dabin Lee ◽  
Jae Joong Kang ◽  
Jae Hyung Lee ◽  
Naeun Jo ◽  
...  
Keyword(s):  
Protein Concentration ◽  
Japan Sea ◽  
Biological Properties ◽  
Measured Data ◽  
Trophic Levels ◽  
Coefficient Of Determination ◽  
P Value ◽  
Chl A ◽  
Major Factors

The cellular macromolecular contents and energy value of phytoplankton as primary food source determine the growth of higher trophic levels, affecting the balance and sustainability of oceanic food webs. Especially, proteins are more directly linked with basic functions of phytoplankton biosynthesis and cell division and transferred through the food chains. In recent years, the East/Japan Sea (EJS) has been changed dramatically in environmental conditions, such as physical and chemical characteristics, as well as biological properties. Therefore, developing an algorithm to estimate the protein concentration of phytoplankton and monitor their spatiotemporal variations on a broad scale would be invaluable. To derive the protein concentration of phytoplankton in EJS, the new regional algorithm was developed by using multiple linear regression analyses based on field-measured data which were obtained from 2012 to 2018 in the southwestern EJS. The major factors for the protein concentration were identified as chlorophyll-a (Chl-a) and sea surface nitrate (SSN) in the southwestern EJS. The coefficient of determination (r2) between field-measured and algorithm-derived protein concentrations was 0.55, which is rather low but reliable. The satellite-derived estimation generally follows the 1:1 line with the field-measured data, with Pearson’s correlation coefficient, which was 0.40 (p-value < 0.01, n = 135). No remarkable trend in the long-term annual protein concentration of phytoplankton was found in the study area during our observation period. However, some seasonal difference was observed in winter protein concentration between the 2003–2005 and 2017–2019 periods. The algorithm is developed for the regional East/Japan Sea (EJS) and could contribute to long-term monitoring for climate-associated ecosystem changes. For a better understanding of spatiotemporal variation in the protein concentration of phytoplankton in the EJS, this algorithm should be further improved with continuous field surveys.

scholarly journals A Conceptual Model of Long-Term Weight Loss Maintenance: The Importance of Cognitive, Empirical and Computational Approaches

2021 ◽  
Vol 18 (2) ◽  
pp. 635
Author(s):  
Darren Haywood ◽  
Blake J. Lawrence ◽  
Frank D. Baughman ◽  
Barbara A. Mullan
Keyword(s):  
Weight Loss ◽  
Weight Loss Maintenance ◽  
Computational Approaches ◽  
Healthy Habits ◽  
Health Related ◽  
The One ◽  
Major Factors ◽  
Positive Social Support ◽  
Weight Loss Interventions

Living with obesity is related to numerous negative health outcomes, including various cancers, type II diabetes, and cardiovascular disease. Although much is known about the factors associated with obesity, and a range of weight loss interventions have been established, changing health-related behaviours to positively affect obesity outcomes has proven difficult. In this paper, we first draw together major factors that have emerged within the literature on weight loss to describe a new conceptual framework of long-term weight loss maintenance. Key to this framework is the suggestion that increased positive social support influences a reduction in psychosocial stress, and that this has the effect of promoting better executive functioning which in turn facilitates the development of healthy habits and the breaking of unhealthy habits, leading to improved ongoing maintenance of weight loss. We then outline how the use of computational approaches are an essential next step, to more rigorously test conceptual frameworks, such as the one we propose, and the benefits that a mixture of conceptual, empirical and computational approaches offer to the field of health psychology.

scholarly journals Senescence-Associated Secretory Phenotype Suppression Mediated by Small-Sized Mesenchymal Stem Cells Delays Cellular Senescence through TLR2 and TLR5 Signaling

Cells ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 63
Author(s):  
Ji Hye Kwon ◽  
Miyeon Kim ◽  
Soyoun Um ◽  
Hyang Ju Lee ◽  
Yun Kyung Bae ◽  
...  
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Cellular Senescence ◽  
Small Cells ◽  
Critical Determinant ◽  
Senescent Phenotype ◽  
Toll Like Receptor 2 ◽  
Secretory Phenotype ◽  
Major Factors

In order to provide a sufficient number of cells for clinical use, mesenchymal stem cells (MSCs) must be cultured for long-term expansion, which inevitably triggers cellular senescence. Although the small size of MSCs is known as a critical determinant of their fate, the main regulators of stem cell senescence and the underlying signaling have not been addressed. Umbilical cord blood-derived MSCs (UCB-MSCs) were obtained using size-isolation methods and then cultured with control or small cells to investigate the major factors that modulate MSC senescence. Cytokine array data suggested that the secretion of interukin-8 (IL-8) or growth-regulated oncogene-alpha (GROa) by senescent cells was markedly inhibited during incubation of small cells along with suppression of cognate receptor (C-X-C motif chemokine receptor2, CXCR2) via blockade of the autocrine/paracrine positive loop. Moreover, signaling via toll-like receptor 2 (TLR2) and TLR5, both pattern recognition receptors, drove cellular senescence of MSCs, but was inhibited in small cells. The activation of TLRs (2 and 5) through ligand treatment induced a senescent phenotype in small cells. Collectively, our data suggest that small cell from UCB-MSCs exhibit delayed cellular senescence by inhibiting the process of TLR signaling-mediated senescence-associated secretory phenotype (SASP) activation.

The Effect of Bench Arrangements on the Natural Ventilation of a Multispan Greenhouse

2013 ◽  
Author(s):  
Sunita Kruger ◽  
Leon Pretorius
Keyword(s):  
Fluid Dynamics ◽  
Natural Ventilation ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Low Velocity ◽  
Lower Velocity ◽  
Cfd Models ◽  
Temperature Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Plant Level

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably. Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.

scholarly journals Long-term prognostic significance of three-dimensional echocardiographic parameters of the left ventricle and left atrium

2009 ◽  
Vol 11 (3) ◽  
pp. 250-256 ◽  
Author(s):  
S. Caselli ◽  
E. Canali ◽  
M. L. Foschi ◽  
D. Santini ◽  
E. Di Angelantonio ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Left Atrium ◽  
Prognostic Significance ◽  
Three Dimensional ◽  
Echocardiographic Parameters

Effect of Load Carrying on Local Dynamic Stability

2007 ◽  
Vol 51 (15) ◽  
pp. 909-913 ◽  
Author(s):  
Jian Liu ◽  
Thurmon E. Lockhart ◽  
Kevin Granata
Keyword(s):  
Dynamic Stability ◽  
Load Condition ◽  
Local Dynamic ◽  
Fall Injuries ◽  
Local Dynamic Stability ◽  
Load Carrying ◽  
Trunk Acceleration ◽  
The Stability ◽  
Major Factors

Occupational load carrying tasks are considered one of the major factors contributing to slip and fall injuries. The objective of the current study was to explore the feasibility to assess the stability changes associated with load carrying by local dynamic stability measures. Twenty-five young participants were involved in a treadmill walking study, with their trunk acceleration profiles measured wirelessly by a tri-axial accelerometer. Finite time local dynamic stability was quantified by maximum Lyapunov exponents (maxLE). The results showed a significant increase in long term maxLE in load condition, indicating the declined local dynamic stability due to the load carrying. Thus, current study confirmed the discriminative validity and sensitivity of local dynamic stability measure and its utility in the load carrying scenario.

scholarly journals Identifying Project Corporate Behavioral Risks to Support Long-Term Sustainable Cooperative Partnerships

2021 ◽  
Vol 13 (11) ◽  
pp. 6347
Author(s):  
Marco Nunes ◽  
António Abreu ◽  
Célia Saraiva
Keyword(s):  
Social Network ◽  
Project Management ◽  
Social Network Analysis ◽  
Network Analysis ◽  
Building Blocks ◽  
Research Literature ◽  
Management Tools ◽  
Dynamic Interactions ◽  
Major Factors

Projects are considered crucial building blocks whereby organizations execute and implement their short-, mid-, and long-term strategic visions. Projects are thought, developed, and implemented to solve problems, drive change, satisfy unique needs, add value, and exploit opportunities, just to name a few objectives. Although existing project management tools and techniques aim to deliver projects with success, according to the latest reviewed literature, projects still keep failing at an impressive pace. Among the extensive list of factors that may threaten project success, several articles from the research literature place particular importance on a still underexplored factor that may strongly lead to unsuccessful project delivery. This factor—usually known as corporate behavioral risks—usually emerges and evolves as organizations work together to deliver projects across a bounded period of time, and is characterized by the mix of formal and informal dynamic interactions between the different stakeholders that constitute the different organizations. Furthermore, several articles from the research literature also point out the lack of proper models to efficiently manage corporate behavioral risks as one of the major factors that may lead to projects failing. To efficiently identify and measure how such corporate behaviors may contribute to a project’s outcomes (success or failure), a heuristic model is proposed in this work, developed based on four fundamental fields ((1) project management, (2) risk management, (3) corporate behavior, and (4) social network analysis), to quantitatively analyze four critical project social networks ((1) communication, (2) problem-solving, (3) advice, and (4) trust), by applying the theory of social network analysis (SNA). The proposed model in this work is supported with a case study to illustrate its implementation and application across a project lifecycle, and how organizations can benefit from its application.

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