Relationship between Some Design Characteristics and Wear in the Bicarbon Heart Valve Prosthesis

1994 ◽  
Vol 17 (5) ◽  
pp. 280-293 ◽  
Author(s):  
P. Arru ◽  
S. Rinaldi ◽  
C. Stacchino ◽  
F. Vallana
Keyword(s):  
Valve Prosthesis ◽  
Impact Wear ◽  
Kinematic Coupling ◽  
Design Characteristics ◽  
Experimental Findings ◽  
Theoretical Considerations ◽  
Valve Model ◽  
Bicarbon Valve ◽  
Bileaflet Valves

The hinge design of a new bileaflet valve (Bicarbon) is presented in relation to the long-term durability characteristics. Theoretical considerations supported by experimental findings, lead to the identification of two different wear mechanisms acting in bileaflet valves, i.e. impact and friction wear. Impact wear, caused by the collision between the hinge stops and inflow surface of the leaflet pivots, is the predominant phenomenon; it is mostly influenced by the design of the coupling elements. The wear due to friction is significantly less important, given a proper kinematic coupling and a thorough washout. These different mechanisms can significantly affect the wear resistance and long-term reliability of bileaflet valves; therefore, they have been properly taken into account in designing the new valve model. The safety of the overall material and design solutions adopted in the Bicarbon valve has been confirmed by extensive accelerated durability tests resulting in no mechanical failure or loss of functionality

Experimente und forstökonomische Fragen

2012 ◽  
Vol 163 (10) ◽  
pp. 417-421
Author(s):  
Urs Fischbacher
Keyword(s):  
Public Goods ◽  
Experimental Method ◽  
Forest Product ◽  
Time Preferences ◽  
Economic Research ◽  
Timber Production ◽  
Markets And Institutions ◽  
Experimental Findings ◽  
Forest Economic

Experiments and forest economic questions During the last decades experiments have gained great importance in economics. These experiments deal with questions that are of significance for forest economic research, too. Timber production, for example, is characterised by long-term decisions and, in addition, forestry produces important public goods. In this article the experimental method is introduced. Furthermore, experimental findings are presented, e.g., concerning time preferences and externalities, and possible applications for the study of forest product markets and institutions are outlined.

scholarly journals Long-term survival after Carpentier-Edwards Perimount aortic valve replacement in Western Denmark: a multi-centre observational study

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Lytfi Krasniqi ◽  
Mads P. Kronby ◽  
Lars P. S. Riber
Keyword(s):  
Risk Factors ◽  
Aortic Valve ◽  
Aortic Valve Replacement ◽  
Valve Replacement ◽  
Significant Risk ◽  
Valve Prosthesis ◽  
Term Survival ◽  
Long Term Survival ◽  
All Cause Mortality

Abstract Background This study describes the long-term survival, risk of reoperation and clinical outcomes of patients undergoing solitary surgical aortic valve replacement (SAVR) with a Carpentier-Edwards Perimount (CE-P) bioprosthetic in Western Denmark. The renewed interest in SAVR is based on the questioning regarding the long-term survival since new aortic replacement technique such as transcatheter aortic-valve replacement (TAVR) probably have shorter durability, why assessment of long-term survival could be a key issue for patients. Methods From November 1999 to November 2013 a cohort of a total of 1604 patients with a median age of 73 years (IQR: 69–78) undergoing solitary SAVR with CE-P in Western Denmark was obtained November 2018 from the Western Danish Heart Registry (WDHR). The primary endpoint was long-term survival from all-cause mortality. Secondary endpoints were survival free from major adverse cardiovascular and cerebral events (MACCE), risk of reoperation, cause of late death, patient-prothesis mismatch, risk of AMI, stroke, pacemaker or ICD implantation and postoperative atrial fibrillation (POAF). Time-to-event analysis was performed with Kaplan-Meier curve, cumulative incidence function was performed with Nelson-Aalen cumulative hazard estimates. Cox regression was applied to detect risk factors for death and reoperation. Results In-hospital mortality was 2.7% and 30-day mortality at 3.4%. The 5-, 10- and 15-year survival from all-cause mortality was 77, 52 and 24%, respectively. Survival without MACCE was 80% after 10 years. Significant risk factors of mortality were small valves, smoking and EuroSCORE II ≥4%. The risk of reoperation was < 5% after 7.5 years and significant risk factors were valve prosthesis-patient mismatch and EuroSCORE II ≥4%. Conclusions Patients undergoing aortic valve replacement with a Carpentier-Edwards Perimount valve shows a very satisfying long-term survival. Future research should aim to investigate biological valves long-term durability for comparison of different SAVR to different TAVR in long perspective.

The potential role of stress and sex steroids in heritable effects of sevoflurane

2021 ◽  
Author(s):  
Anatoly E Martynyuk ◽  
Ling-Sha Ju ◽  
Timothy E Morey
Keyword(s):  
Sex Steroids ◽  
Age Groups ◽  
Postnatal Period ◽  
Health Concern ◽  
General Anesthetics ◽  
Pharmacological Agents ◽  
Experimental Findings ◽  
Heritable Effects

Abstract Most surgical procedures require general anesthesia, which is a reversible deep sedation state lacking all perception. The induction of this state is possible because of complex molecular and neuronal network actions of general anesthetics (GAs) and other pharmacological agents. Laboratory and clinical studies indicate that the effects of GAs may not be completely reversible upon anesthesia withdrawal. The long-term neurocognitive effects of GAs, especially when administered at the extremes of ages, are an increasingly recognized health concern and the subject of extensive laboratory and clinical research. Initial studies in rodents suggest that the adverse effects of GAs, whose actions involve enhancement of GABA type A receptor activity (GABAergic GAs), can also extend to future unexposed offspring. Importantly, experimental findings show that GABAergic GAs may induce heritable effects when administered from the early postnatal period to at least young adulthood, covering nearly all age groups that may have children after exposure to anesthesia. More studies are needed to understand when and how the clinical use of GAs in a large and growing population of patients can result in lower resilience to diseases in the even larger population of their unexposed offspring. This minireview is focused on the authors’ published results and data in the literature supporting the notion that GABAergic GAs, in particular sevoflurane, may upregulate systemic levels of stress and sex steroids and alter expressions of genes that are essential for the functioning of these steroid systems. The authors hypothesize that stress and sex steroids are involved in the mediation of sex-specific heritable effects of sevoflurane.

In patients undergoing dialysis who require a valve replacement is a bioprosthetic valve superior to a mechanical prosthesis in terms of long-term survival and morbidity?

2020 ◽  
Vol 31 (2) ◽  
pp. 174-178
Author(s):  
Laura S Fong ◽  
Zhen Hao Ang ◽  
Hugh Wolfenden ◽  
Zakir Akhunji
Keyword(s):  
Valve Replacement ◽  
Mechanical Valve ◽  
High Risk Group ◽  
Bioprosthetic Valve ◽  
Valve Prosthesis ◽  
Mechanical Prosthesis ◽  
Term Survival ◽  
Long Term Survival ◽  
Significant Difference

Abstract A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was ‘In [dialysis patients undergoing a valve replacement] is [a bioprosthetic valve superior to a mechanical prosthesis] for [long-term survival and morbidity]’. Altogether more than 501 papers were found using the reported search, of which five represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. There was limited high-quality evidence with all studies being retrospective. One meta-analysis and four cohort studies provided the evidence that there was no significant difference in long-term survival based on prosthesis type. However, the majority of studies demonstrated a significantly higher rate of valve-related complications including bleeding and thromboembolism, and readmission to hospital in the mechanical valve prosthesis group, likely related to the requirement for long-term anticoagulation. We conclude that overall long-term survival in dialysis-dependent patients is poor. While prosthesis type does not play a significant contributing role to long-term survival, bioprosthetic valves were associated with significantly fewer valve-related complications. Based on the available evidence, a bioprosthetic valve may be more suitable in this high-risk group of patients as it may avoid the complications associated with long-term anticoagulation without any reduction in long-term survival.

Listening to the child victim of abuse through the process of therapy: A case study

2001 ◽  
Vol 26 (3) ◽  
pp. 18-22 ◽  
Author(s):  
Neerosh Mudaly ◽  
Chris Goddard
Keyword(s):  
Therapeutic Process ◽  
Young Person ◽  
Response To Therapy ◽  
Child Victim ◽  
To Come ◽  
Long Term Impact ◽  
The Impact ◽  
Theoretical Considerations

When a child has been abused by his or her father or father-figure and makes the statement ‘I want Dad to come home’, whose voice are we hearing in treatment, how do we interpret and respond to what the child is saying? Understanding and responding to the voices of victims of abuse is a complex issue. This paper explores the issues of listening to and responding to a young vicitm of abuse in the context of the impact of the abuse on this young person, and how these issues emerged and were addressed in the therapeutic process. Amanda, a 13-year-old girl, disclosed sexual abuse by her stepfather. In the initial months of counselling she repeatedly expressed her wish for her stepfather to return home. Amanda’s response to therapy, the short-term and long-term impact issues that were addressed, and the various therapeutic techniques that were used to assist in her recovery, are traced in the context of theoretical considerations.

Alert system design based on experimental findings from long-term unobtrusive monitoring in COPD

2021 ◽  
Vol 63 ◽  
pp. 102205
Author(s):  
A.C. den Brinker ◽  
R. van Dinther ◽  
M.G. Crooks ◽  
S. Thackray-Nocera ◽  
A.H. Morice
Keyword(s):  
System Design ◽  
Alert System ◽  
Experimental Findings

Are There Different Kinds of Rogue Waves?

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Paul C. Liu ◽  
Keith R. MacHutchon
Keyword(s):  
Rogue Wave ◽  
Rogue Waves ◽  
Rayleigh Distribution ◽  
The Other ◽  
South Indian Ocean ◽  
Gas Drilling ◽  
Wave Measurements ◽  
South Indian ◽  
Theoretical Considerations

There is clearly no immediate answer to the question posted by the title of this paper. Inasmuch as that there are not much definitively known about rogue waves and that there is still no universally accepted definition for rogue waves in the ocean, we think there might just be even more than one kind of rogue waves to contend with. While the conventional approach has generally designated waves with Hmax∕Hs greater than 2.2 as possible rogue waves, based on Rayleigh distribution considerations, there is conspicuously no provision as to how high the ratio of Hmax∕Hs can be and thus not known how high can a rogue wave be. In our analysis of wave measurements made from a gas-drilling platform in South Indian Ocean, offshore from Mossel Bay, South Africa, we found a number of cases that indicated Hmax∕Hs could be valued in the range between 4 and 10. If this were to be the case, then these records could be considered to be “uncommon” rogue waves, whereas a record of Hmax∕Hs in the range between 2 and 4 could be considered to comprise “typical” rogue waves. On the other hand, the spikes in the Hmax data could have been caused by equipment malfunction or some other phenomenon. Clearly, the question of whether or not there are different kinds of rogue waves cannot be readily answered by theoretical considerations alone and there is a crucial need for long-term wave time-series measurements for studying rogue waves.

Being Suspicious of the Sense of Ease and Undeterred by the Sense of Difficulty: Looking Back at Schmidt and Bjork (1992)

2018 ◽  
Vol 13 (2) ◽  
pp. 146-148 ◽  
Author(s):  
Robert A. Bjork
Keyword(s):  
Verbal Learning ◽  
Training Needs ◽  
Term Retention ◽  
New Concepts ◽  
Rate Of Learning ◽  
Long Term Retention ◽  
Experimental Findings ◽  
Teaching Learning ◽  
And Training

Richard Schmidt and I titled our article “New Conceptualizations of Practice: Common Principles in Three Paradigms Suggest New Concepts for Training” to reflect our view that prevailing ideas about how to optimize teaching, learning, and practicing were, in our words, “at best incomplete, and at worst incorrect.” We argued that teachers and trainers were susceptible to being misled by two commonsense assumptions—namely, that procedures that enhance performance during training are the procedures of choice and that the context of training needs to match in detail the posttraining context that is the target of training. A variety of then-recent experimental findings challenged both assumptions and demonstrated, in particular, that procedures posing certain difficulties and appearing to slow the rate of learning often enhanced long-term retention and transfer of to-be-learned skills and knowledge. Given the parallel nature of such findings for both motor and verbal learning, we concluded that principles of considerable generality could be deduced to upgrade teaching and training.

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