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Evolutionary radiations of woody taxa within arid environments were made possible by multiple trait innovations including deep roots and embolism-resistant xylem, but little is known about how these traits have coevolved across the phylogeny of woody plants or how they jointly influence the distribution of species. We synthesized global trait and vegetation plot datasets to examine how rooting depth and xylem vulnerability across 188 woody plant species interact with aridity, precipitation seasonality, and water table depth to influence species occurrence probabilities across all biomes. Xylem resistance to embolism and rooting depth are independent woody plant traits that do not exhibit an interspecific trade-off. Resistant xylem and deep roots increase occurrence probabilities in arid, seasonal climates over deep water tables. Resistant xylem and shallow roots increase occurrence probabilities in arid, nonseasonal climates over deep water tables. Vulnerable xylem and deep roots increase occurrence probabilities in arid, nonseasonal climates over shallow water tables. Lastly, vulnerable xylem and shallow roots increase occurrence probabilities in humid climates. Each combination of trait values optimizes occurrence probabilities in unique environmental conditions. Responses of deeply rooted vegetation may be buffered if evaporative demand changes faster than water table depth under climate change.
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Embolia , Agua Subterránea , Agua/fisiología , Madera/fisiología , Xilema/fisiología , Plantas , Hojas de la Planta/fisiología , SequíasRESUMEN
Background: A clinical study comparing the hemodynamic outcomes of transcatheter mitral valve replacement (TMVR) with vs. without Laceration of the Anterior Mitral leaflet to Prevent Outflow Obstruction (LAMPOON) has never been designed nor conducted. Aims: To quantify the hemodynamic impact of LAMPOON in TMVR using patient-specific computational (in silico) models. Materials: Eight subjects from the LAMPOON investigational device exemption trial were included who had acceptable computed tomography (CT) data for analysis. All subjects were anticipated to be at prohibitive risk of left ventricular outflow tract (LVOT) obstruction from TMVR, and underwent successful LAMPOON immediately followed by TMVR. Using post-procedure CT scans, two 3D anatomical models were created for each subject: (1) TMVR with LAMPOON (performed procedure), and (2) TMVR without LAMPOON (virtual control). A validated computational fluid dynamics (CFD) paradigm was then used to simulate the hemodynamic outcomes for each condition. Results: LAMPOON exposed on average 2 ± 0.6 transcatheter valve cells (70 ± 20 mm2 total increase in outflow area) which provided an additional pathway for flow into the LVOT. As compared to TMVR without LAMPOON, TMVR with LAMPOON resulted in lower peak LVOT velocity, lower peak LVOT gradient, and higher peak LVOT effective orifice area by 0.4 ± 0.3 m/s (14 ± 7% improvement, p = 0.006), 7.6 ± 10.9 mmHg (31 ± 17% improvement, p = 0.01), and 0.2 ± 0.1 cm2 (17 ± 9% improvement, p = 0.002), respectively. Conclusion: This was the first study to permit a quantitative, patient-specific comparison of LVOT hemodynamics following TMVR with and without LAMPOON. The LAMPOON procedure achieved a critical increment in outflow area which was effective for improving LVOT hemodynamics, particularly for subjects with a small neo-left ventricular outflow tract (neo-LVOT).
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PURPOSE: This study quantitatively evaluated the phasic right heart morphology of candidate patients for a transcatheter tricuspid valve intervention (N=32) and of subjects with trace to no tricuspid regurgitation (N = 14). METHODS: Cardiac computed tomography angiography (CCTA) and transthoracic/transesophageal echocardiography (TTE/TEE) images were analyzed using dedicated research and clinical software. Using CCTA, the phasic right atrial and ventricular volumes, annulus dimensions, annulus-to-right coronary artery (RCA) distances, circumferential topography of the annular tissue shelf, vena cava dimensions (inferior and superior), vena cava positions, axis angles, and annular excursions were quantified. Using TTE/TEE, leaflet geometry, regurgitation, hemodynamics, and heart function were quantified. Measurements within and between groups were quantitatively compared with regression analyses to explore relationships between right heart features. RESULTS: The phasic position and orientation of the vena cava and the circumferential topography of the annular tissue shelf were quantitatively presented for the first time. The candidate patient group exhibited greater chamber dimensions, enlarged vena cava, distended vena cava positions, positional shallowing of the annular tissue shelf, geometric annular distortion, leaflet distention, moderate or greater regurgitation, and impaired ventricular function. Atrial volume correlated strongly with directional vena cava positions as well as with annular dimensions. Annulus-to-RCA distances and annular excursions were comparable between groups. CONCLUSIONS: This study provides new and further insight to the right heart morphology and functional characteristics of candidate patients for a transcatheter tricuspid valve intervention. These data provide a platform from which these patients can continue to be better understood for further improving transcatheter system design and use.
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Insuficiencia de la Válvula Tricúspide , Válvula Tricúspide , Angiografía por Tomografía Computarizada/métodos , Ecocardiografía , Hemodinámica , Humanos , Válvula Tricúspide/diagnóstico por imagen , Válvula Tricúspide/cirugía , Insuficiencia de la Válvula Tricúspide/diagnóstico por imagen , Insuficiencia de la Válvula Tricúspide/cirugíaRESUMEN
Modern coexistence theory holds that stabilizing mechanisms, whereby species limit the growth of conspecifics more than that of other species, are necessary for species to coexist. Here, we used experimental and observational approaches to assess stabilizing forces in eight locally co-occurring, annual, legume species in the genus Trifolium. We experimentally measured self-limitation in the field by transplanting Trifolium species into each other's field niches while varying competition and related these patterns to the field coexistence dynamics of natural Trifolium populations. We found that Trifolium species differed in their responses to local environmental gradients and performed best in their home environments, consistent with habitat specialization and presenting a possible barrier to coexistence at fine scales. We found significant self-limitation for 5 of 42 pairwise species combinations measured experimentally with competitors absent, indicating stabilization through plant-soil feedbacks and other indirect interactions, whereas self-limitation was largely absent when neighbors were present, indicating destabilizing effects of direct plant-plant interactions. The degree of self-limitation measured in our field experiment explained year-to-year dynamics of coexistence by Trifolium species in natural communities. By assessing stabilizing forces and environmental responses in the full n-dimensional field niche, this study sheds light on the roles of habitat specialization, plant-soil feedbacks, and plant interactions in determining species coexistence at local scales.
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Ecosistema , Suelo , Trifolium/crecimiento & desarrollo , PlantasRESUMEN
Coexistence requires that stabilizing niche differences, which cause species to limit themselves more than others, outweigh relative fitness differences, which cause competitive exclusion. Interactions with shared mutualists, which can differentially affect host fitness and change in magnitude with host frequency, can satisfy these conditions for coexistence, yet empirical tests of mutualist effects on relative fitness and stabilizing niche differences are largely lacking within the framework of coexistence theory. Here, we show that N-fixing rhizobial mutualists mediate coexistence in four naturally co-occurring congeneric legume (Trifolium) species. Using experimental greenhouse communities, we quantified relative fitness and stabilizing niche differences for each species in the presence of rhizobia originating from conspecific or congeneric hosts. Rhizobia stabilized coexistence by increasing the self-limitation of Trifolium species grown with rhizobia isolated from conspecifics, thus allowing congeners to increase when rare. Greenhouse-measured invasion growth rates predicted natural, unmanipulated coexistence dynamics of Trifolium species over 2 years at our field sites. Our results demonstrate that interactions with shared mutualists can stabilize the coexistence of closely related species.
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Nodulación de la Raíz de la Planta , Rhizobium leguminosarum/fisiología , Trifolium/microbiología , Especificidad de la Especie , Simbiosis , Trifolium/crecimiento & desarrolloRESUMEN
In the interventional treatment of tricuspid valve regurgitation, the majority of prosthetic devices interact with or are implanted to the tricuspid valve annulus. For new transcatheter technologies, there exists a growing body of clinical experience, literature, and professional discourse related to the difficulties in delivering, securing, and sustaining the function of these devices within the dynamic tricuspid annulus. Many of the difficulties arise from circumstances not encountered in open-heart surgery, namely; a non-arrested heart, indirect visualization, and a reliance on non-suture-based methods. These challenges require the application of procedural techniques or system designs to account for tricuspid annular motion, forces, and underlying tissue strength. Improved knowledge in these interactions will support the goals of improving device systems, their procedures, and patient outcomes. This review aims to describe current concepts of tricuspid annular mechanics, key device and procedural implications, and highlight current knowledge gaps for future consideration.
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Cateterismo Cardíaco/instrumentación , Anuloplastia de la Válvula Cardíaca/instrumentación , Implantación de Prótesis de Válvulas Cardíacas/instrumentación , Prótesis Valvulares Cardíacas , Hemodinámica , Insuficiencia de la Válvula Tricúspide/cirugía , Válvula Tricúspide/cirugía , Animales , Fenómenos Biomecánicos , Cateterismo Cardíaco/efectos adversos , Anuloplastia de la Válvula Cardíaca/efectos adversos , Implantación de Prótesis de Válvulas Cardíacas/efectos adversos , Implantación de Prótesis de Válvulas Cardíacas/métodos , Humanos , Diseño de Prótesis , Recuperación de la Función , Resultado del Tratamiento , Válvula Tricúspide/diagnóstico por imagen , Válvula Tricúspide/fisiopatología , Insuficiencia de la Válvula Tricúspide/diagnóstico por imagen , Insuficiencia de la Válvula Tricúspide/fisiopatologíaRESUMEN
Understanding patterns of functional trait variation across environmental gradients offers an opportunity to increase inference in the mechanistic causes of plant community assembly. The leaf economics spectrum (LES) predicts global tradeoffs in leaf traits and trait-environment relationships, but few studies have examined whether these predictions hold across different levels of organization, particularly within species. Here, we asked (1) whether the main assumptions of the LES (expected trait relationships and shifts in trait values across resource gradients) hold at the intraspecific level, and (2) how within-species trait correlations scale up to interspecific or among-community levels. We worked with leaf traits of saplings of woody species growing across light and soil N and P availability gradients in temperate rainforests of southern Chile. We found that ITV accounted for a large proportion of community-level variation in leaf traits (e.g., LMA and leaf P) and played an important role in driving community-level shifts in leaf traits across environmental gradients. Additionally, intraspecific leaf trait relationships were generally consistent with interspecific and community-level trait relationships and with LES predictions-e.g., a strong negative intraspecific LMA-leaf N correlation-although, most trait relationships varied significantly among species, suggesting idiosyncrasies in the LES at the intraspecific level.
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Hojas de la Planta , Suelo , Chile , Fenotipo , Bosque LluviosoRESUMEN
OBJECTIVE: The study objective was to quantify the effect of ring type, ring-annulus sizing, suture position, and surgeon on the forces required to tie down and constrain a mitral annuloplasty ring to a beating heart. METHODS: Physio (Edwards Lifesciences, Irvine, Calif) or Profile 3D (Medtronic, Dublin, Ireland) annuloplasty rings were instrumented with suture force transducers and implanted in ovine subjects (N = 23). Tie-down forces and cyclic contractile forces were recorded and analyzed at 10 suture positions and at 3 levels of increasing peak left ventricular pressure. RESULTS: Across all conditions, tie-down force was 2.7 ± 1.4 N and cyclic contractile force was 2.0 ± 1.2 N. Tie-down force was not meaningfully affected by any factor except surgeon. Significant differences in overall and individual tie-down forces were observed between the 2 primary implanting surgeons. No other factors were observed to significantly affect tie-down force. Contractile suture forces were significantly reduced by ring-annulus true sizing. This was driven almost exclusively by Physio cases and by reduction along the anterior aspect, where dehiscence is less common clinically. Contractile suture forces did not differ significantly between ring types. However, when undersizing, Profile 3D forces were significantly more uniform around the annular circumference. A suture's tie-down force did not correlate to its eventual contractile force. CONCLUSIONS: Mitral annuloplasty suture loading is influenced by ring type, ring-annulus sizing, suture position, and surgeon, suggesting that reports of dehiscence may not be merely a series of isolated errors. When compared with forces known to cause suture dehiscence, these in vivo suture loading data aid in establishing potential targets for reducing the occurrence of ring dehiscence.
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Anuloplastia de la Válvula Mitral , Insuficiencia de la Válvula Mitral/cirugía , Válvula Mitral , Ajuste de Prótesis , Técnicas de Sutura , Animales , Prótesis Valvulares Cardíacas/efectos adversos , Válvula Mitral/patología , Válvula Mitral/cirugía , Anuloplastia de la Válvula Mitral/efectos adversos , Anuloplastia de la Válvula Mitral/instrumentación , Anuloplastia de la Válvula Mitral/métodos , Modelos Anatómicos , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/prevención & control , Diseño de Prótesis/métodos , Ajuste de Prótesis/efectos adversos , Ajuste de Prótesis/métodos , OvinosRESUMEN
BACKGROUND AND AIMS: Ecologists are increasingly using plant functional traits to predict community assembly, but few studies have linked functional traits to species' responses to fine-scale resource gradients. In this study, it was tested whether saplings of woody species partition fine-scale gradients in light availability based on their leaf mass per area (LMA) in three temperate rain forests and one Mediterranean forest in southern Chile. METHODS: LMA was measured under field conditions of all woody species contained in approx. 60 plots of 2 m2 in each site, and light availability, computed as the gap light index (GLI), was determined. For each site, species' pairwise differences in mean LMA (Δ LMA) and abundance-weighted mean GLI (Δ light response) of 2 m2 plots were calculated and it was tested whether they were positively related using Mantel tests, i.e. if species with different LMA values differed in their response to light availability. Additionally linear models were fitted to the relationship between plot-level mean LMA and GLI across plots for each site. KEY RESULTS: A positive and significant relationship was found between species' pairwise differences in mean LMA and differences in light response across species for all temperate rain forests, but not for the Mediterranean forest. The results also indicated a significant positive interspecific link between LMA and light availability for all forests. This is in contrast to what is traditionally reported and to expectations from the leaf economics spectrum. CONCLUSIONS: In environments subjected to light limitation, interspecific differences in a leaf trait (LMA) can explain the fine-scale partitioning of light availability gradients by woody plant species. This niche partitioning potentially facilitates species coexistence at the within-community level. The high frequency of evergreen shade-intolerant species in these forests may explain the positive correlation between light availability and LMA.
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Ecosistema , Hojas de la Planta/anatomía & histología , Bosque Lluvioso , Luz Solar , Adaptación Fisiológica , Hojas de la Planta/fisiología , Plantas/anatomía & histologíaRESUMEN
BACKGROUND: Annuloplasty ring dehiscence is a well described mode of mitral valve repair failure. Defining the mechanisms underlying dehiscence may facilitate its prevention. METHODS: Factors that govern suture dehiscence were examined with an ovine model. After undersized ring annuloplasty in live animals (n = 5), cyclic force (FC) that acts on sutures during cardiac contraction was measured with custom transducers. FC was measured at ten suture positions, throughout cardiac cycles with peak left ventricular pressure (LVPmax) of 100, 125, and 150 mm Hg. Suture pullout testing was conducted on explanted mitral annuli (n = 12) to determine suture holding strength at each position. Finally, relative collagen density differences at suture sites around the annulus were assessed by two-photon excitation fluoroscopy. RESULTS: Anterior FC exceeded posterior FC at each LVPmax (eg, 2.8 ± 1.3 N versus 1.8 ± 1.2 N at LVPmax = 125 mm Hg, p < 0.01). Anterior holding strength exceeded posterior holding strength (6.4 ± 3.6 N versus 3.9 ± 1.6 N, p < 0.0001). On the basis of FC at LVPmax of 150 mm Hg, margin of safety before suture pullout was vastly higher between the trigones (exclusive) versus elsewhere (4.8 ± 0.9 N versus 1.9 ± 0.5 N, p < 0.001). Margin of safety exhibited strong correlation to collagen density (R(2) = 0.947). CONCLUSIONS: Despite lower cyclic loading on posterior sutures, the weaker posterior mitral annular tissue creates higher risk of dehiscence, apparently because of reduced collagen content. Sutures placed atop the trigones are less secure than predicted, because of a combination of reduced collagen and higher overall rigidity in this region. These findings highlight the inter-trigonal tissue as the superior anchor and have implications on the design and implantation techniques for next-generation mitral prostheses.
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Colágeno/metabolismo , Prótesis Valvulares Cardíacas , Anuloplastia de la Válvula Mitral/métodos , Válvula Mitral/cirugía , Complicaciones Posoperatorias , Técnicas de Sutura/instrumentación , Suturas , Animales , Modelos Animales de Enfermedad , Insuficiencia de la Válvula Mitral/cirugía , Diseño de Prótesis , OvinosRESUMEN
A basic assumption of the trait-based approach in plant ecology is that differences in functional trait values are greater between species than within species. We questioned this assumption by assessing (1) the relative extent of inter- and intraspecific leaf trait variation throughout a complete growing season (phenological variation) in a group of deciduous and evergreen woody species, and (2) whether species rankings based on leaf traits were maintained across the growing season. We analysed leaf mass per area (LMA) and leaf nutrient concentrations (C, N, P), including the C:N and N:P ratios. Intraspecific trait variation (ITV) due to phenology was significantly greater than interspecific variation for leaf N concentration on a mass basis (Nm; 68.90 %) and for the leaf C:N ratio (60.60 %), whereas interspecific variation was significantly higher than ITV for LMA (62.30 %) and for leaf C concentration on a mass (Cm) and area (Ca) basis (Cm 70.40 %; Ca 65.30 %). ITV was particularly low for LMA (<20 %). Species rankings were highly modified by phenology for a number of leaf traits (Pm, N:P ratio) but were relatively well conserved throughout the growing season for others (LMA, Nm). Patterns of ITV across the growing season differed significantly between deciduous and evergreen species for all traits except leaf P but did not vary between native and exotic species. Overall, our results show that intraspecific phenological variation in leaf traits may be similar to or greater than interspecific variation and that temporal patterns of ITV vary considerably among traits and species, especially for leaf nutrient concentrations, factors which can potentially affect quantitative interspecific relationships.
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Hojas de la Planta/anatomía & histología , Hojas de la Planta/química , Árboles/fisiología , Biodiversidad , Carbono/análisis , Nitrógeno/análisis , Fenotipo , Fósforo/análisis , Estaciones del Año , Especificidad de la Especie , Árboles/anatomía & histología , Árboles/químicaRESUMEN
Environmental changes are expected to shift the distribution of functional trait values in plant communities through a combination of species turnover and intraspecific variation. The strength of these shifts may depend on the availability of individuals with trait values adapted to new environmental conditions, represented by the functional diversity (FD) of existing community residents or dispersal from the regional species pool. We conducted a 3-year nutrient- and seed-addition experiment in old-field plant communities to examine the contributions of species turnover and intraspecific variation to community trait shifts, focusing on four key plant functional traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We further examined the influence of initial FD and seed availability on the strength of these shifts. Community mean height, leaf area, and SLA increased in response to fertilization, and these shifts were driven almost entirely by intraspecific variation. The strength of intraspecific shifts in height and leaf area was positively related to initial intraspecific FD in these traits. Intraspecific trait responses to fertilization varied among species, with species of short stature displaying stronger shifts in SLA and LDMC but weaker shifts in leaf area. Trait shifts due to species turnover were generally weak and opposed intraspecific responses. Seed addition altered community taxonomic composition but had little effect on community trait shifts. These results highlight the importance of intraspecific variation for short-term community functional responses and demonstrate that the strength of these responses may be mediated by community FD.
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Biota , Fertilización , Pradera , Magnoliopsida/fisiología , Ambiente , Magnoliopsida/crecimiento & desarrollo , New York , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/fisiologíaRESUMEN
Rapid preclinical evaluations of mitral valve (MV) mechanics are currently best facilitated by bench models of the left ventricle (LV). This review aims to provide a comprehensive assessment of these models to aid interpretation of their resulting data, inform future experimental evaluations, and further the translation of results to procedure and device development. For this review, two types of experimental bench models were evaluated. Rigid LV models were characterized as fluid-mechanical systems capable of testing explanted MVs under static and or pulsatile left heart hemodynamics. Passive LV models were characterized as explanted hearts whose left side is placed in series with a static or pulsatile flow-loop. In both systems, MV function and mechanics can be quantitatively evaluated. Rigid and passive LV models were characterized and evaluated. The materials and methods involved in their construction, function, quantitative capabilities, and disease modeling were described. The advantages and disadvantages of each model are compared to aid the interpretation of their resulting data and inform future experimental evaluations. Repair and percutaneous studies completed in these models were additionally summarized with perspective on future advances discussed. Bench models of the LV provide excellent platforms for quantifying MV repair mechanics and function. While exceptional work has been reported, more research and development is necessary to improve techniques and devices for repair and percutaneous surgery. Continuing efforts in this field will significantly contribute to the further development of procedures and devices, predictions of long-term performance, and patient safety.
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Implantación de Prótesis de Válvulas Cardíacas/métodos , Insuficiencia de la Válvula Mitral/fisiopatología , Insuficiencia de la Válvula Mitral/cirugía , Válvula Mitral/fisiopatología , Válvula Mitral/cirugía , Procedimientos Quirúrgicos Cardíacos/instrumentación , Procedimientos Quirúrgicos Cardíacos/métodos , Ablación por Catéter/métodos , Simulación por Computador , Ecocardiografía Doppler , Implantación de Prótesis de Válvulas Cardíacas/efectos adversos , Humanos , Fenómenos Mecánicos , Válvula Mitral/anatomía & histología , Válvula Mitral/patología , Insuficiencia de la Válvula Mitral/patología , Modelos Cardiovasculares , Diseño de Prótesis , Flujo Pulsátil/fisiologíaRESUMEN
Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the total trait variation among communities on average. The relative extent of ITV tended to be greater for whole-plant (e.g. plant height) vs. organ-level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait-based community and ecosystem studies.
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Biodiversidad , Fenotipo , Fenómenos Fisiológicos de las Plantas , Especificidad de la EspecieRESUMEN
Computational models for the heart's mitral valve (MV) exhibit several uncertainties that may be reduced by further developing these models using ground-truth data-sets. This study generated a ground-truth data-set by quantifying the effects of isolated mitral annular flattening, symmetric annular dilatation, symmetric papillary muscle (PM) displacement and asymmetric PM displacement on leaflet coaptation, mitral regurgitation (MR) and anterior leaflet strain. MVs were mounted in an in vitro left heart simulator and tested under pulsatile haemodynamics. Mitral leaflet coaptation length, coaptation depth, tenting area, MR volume, MR jet direction and anterior leaflet strain in the radial and circumferential directions were successfully quantified at increasing levels of geometric distortion. From these data, increase in the levels of isolated PM displacement resulted in the greatest mean change in coaptation depth (70% increase), tenting area (150% increase) and radial leaflet strain (37% increase) while annular dilatation resulted in the largest mean change in coaptation length (50% decrease) and regurgitation volume (134% increase). Regurgitant jets were centrally located for symmetric annular dilatation and symmetric PM displacement. Asymmetric PM displacement resulted in asymmetrically directed jets. Peak changes in anterior leaflet strain in the circumferential direction were smaller and exhibited non-significant differences across the tested conditions. When used together, this ground-truth data-set may be used to parametrically evaluate and develop modelling assumptions for both the MV leaflets and subvalvular apparatus. This novel data may improve MV computational models and provide a platform for the development of future surgical planning tools.
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Insuficiencia de la Válvula Mitral/fisiopatología , Válvula Mitral/fisiopatología , Animales , Fenómenos Biomecánicos , Simulación por Computador , Dilatación Patológica , Corazón/fisiología , Hemodinámica , Modelos Cardiovasculares , Músculos Papilares/fisiopatología , OvinosRESUMEN
Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields) across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.
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Biodiversidad , Cambio Climático , Poaceae/fisiología , Suelo , California , New York , South CarolinaRESUMEN
PURPOSE: To demonstrate the first use of a novel technology for quantifying suture forces on annuloplasty rings to better understand the mechanisms of ring dehiscence. DESCRIPTION: Force transducers were developed, attached to a size 24 Physio ring, and implanted in the mitral annulus of an ovine animal. Ring suture forces were measured after implantation and for cardiac cycles reaching peak left ventricular pressures (LVP) of 100, 125, and 150 mm Hg. EVALUATION: After implantation of the undersized ring to the flaccid annulus, the mean suture force was 2.0±0.6 N. During cyclic contraction, the anterior ring suture forces were greater than the posterior ring suture forces at peak LVPs of 100 mm Hg (4.9±2.0 N vs 2.1±1.1 N), 125 mm Hg (5.4±2.3 N vs 2.3±1.2 N), and 150 mm Hg (5.7±2.4 N vs 2.4±1.1 N). The largest force was 7.4 N at 150 mm Hg. CONCLUSIONS: The preliminary results demonstrate trends in annuloplasty suture forces and their variation with location and LVP. Future studies will significantly contribute to clinical knowledge by elucidating the mechanisms of ring dehiscence while improving annuloplasty ring design and surgical repair techniques.