The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Curtis D. Holder - One of the best experts on this subject based on the ideXlab platform.
-
Leaf Water Repellency as an Adaptation to Tropical Montane Cloud Forest Environments
Biotropica, 2007Co-Authors: Curtis D. HolderAbstract:Adaptations that reduce water retention on leaf surfaces may increase photosynthetic capacity of cloud forests because carbon dioxide diffuses slower in water than air. Leaf water repellency was examined in three distinct ecosystems to test the hypothesis that tropical montane cloud forest species have a higher degree of leaf water repellency than species from tropical dry forests and species from temperate foothills-grassland vegetation. Leaf water repellency was measured by calculating the contact angle of the leaf surface and the Line Tangent to a water droplet through the point of contact on the adaxial and the abaxial surface. Leaf water repellency was significantly different between the three study areas. The hypothesis that leaf water repellency is higher in cloud forest species than tropical dry forests and temperate foothills-grassland vegetation was not confirmed in this study. Leaf water repellency was lower for cloud forest species (adaxial surface = 50.8°; abaxial surface = 82.9°) than tropical dry forest species (adaxial surface = 74.5°; abaxial surface = 87.3°) and temperate foothills-grassland species (adaxial surface = 77.6°; abaxial surface = 95.8°). The low values of leaf water repellency in cloud forest species may be influenced by presence of epiphylls and loss of epicuticular wax on the leaf surfaces.
-
Leaf water repellency of species in Guatemala and Colorado (USA) and its significance to forest hydrology studies
Journal of Hydrology, 2007Co-Authors: Curtis D. HolderAbstract:Summary Fog persistency and high precipitation totals contribute to the unique ecohydrology of tropical montane cloud forests. The persistence of water droplets on leaf surfaces in cloud forests inhibits photosynthetic carbon exchange because carbon dioxide diffuses slower in water than air. Adaptations that reduce water retention on leaf surfaces may increase photosynthetic capacity of cloud forests. The objective of the present study was to determine if 12 cloud forest species from the Sierra de las Minas, Guatemala have a higher degree of leaf water repellency than 12 species from tropical dry forests in Chiquimula, Guatemala and 12 species from foothills–grassland vegetation in Colorado (USA). Leaf water repellency was measured as the contact angle between the leaf surface and the Line Tangent to the water droplet passing through the point of contact between the droplet and the leaf surface. Analysis of variance indicated that leaf water repellency was significantly different between the three study areas; however, the leaf water repellency of 12 species in the Sierra de las Minas was lower than 12 species in Chiquimula and lower than the leaf water repellency of 12 species in Colorado. Leaf water repellency of abaxial surfaces of all species in the cloud forest (Sierra de las Minas) was greater leaf water repellency of adaxial surfaces. The low values of leaf water repellency in cloud forest species may be influenced by presence of epiphylls or the loss of epicuticular wax on the leaf surfaces because of high precipitation totals and longer leaf life-span. High leaf water repellency in dry climates may be an adaptation to increase hydrological inputs underneath the canopy.
Oliver Kessler - One of the best experts on this subject based on the ideXlab platform.
-
A useful radiologic method for preoperative joint-Line determination in revision total knee arthroplasty.
Clinical Orthopaedics and Related Research®, 2009Co-Authors: José Romero, Burkhardt Seifert, Olaf Reinhardt, Oliver Ziegler, Oliver KesslerAbstract:Intraoperative joint-Line determination during revision TKA is difficult and no method exists to plan the position preoperatively. Two questions need to be answered: to which extent does the joint Line differ from its anatomic position after revision TKA if it has only been determined intraoperatively, and can the joint Line be calculated preoperatively based on the transepicondylar width. Of 22 consecutive patients with complete preoperative (before and after primary TKA) and postoperative (after revision TKA) radiograph documentation, the joint-Line position was measured on plane radiographs using the medial epicondyle as a reference. On another set of 45 consecutive patients with no knee disorders other than meniscal lesions, the transepicondylar axis width (TEAW) and the perpendicular distance from the medial and lateral epicondyles to the joint Line were measured twice by two independent observers on plane AP radiographs of the knee. Significant joint-Line alterations were observed after primary and revision TKA, implicating that a method for preoperative planning is needed. Because a Linear correlation between the TEAW and the perpendicular distance from the epicondyles to the joint-Line Tangent was found, the ratio is useful to calculate the true joint-Line position from the TEAW before revision TKA.
Cristina Bonora - One of the best experts on this subject based on the ideXlab platform.
-
Preoperative assisted navigation for total knee arthroplasty (TKA) : preliminary results
Knee Surgery Sports Traumatology Arthroscopy, 2012Co-Authors: Valerio Sansone, N. Ursino, Cristina BonoraAbstract:Objectives: Aims of the study were to assess the sagittal tibial slope and posterior offset of femoral condyles and whether any correlation between the two is present. In particular, we hypothesized that the degree of posterior tibial slope is related to the posterior offset of femoral condyles to achieve adequate joint motion and stability during the flexion of the knee. Methods: We evaluated the magnetic resonance studies of the knees of 80 subjects, 45 males and 35 females, with an average age of 38.9 years, to assess the variability of posterior condylar offset and sagittal tibial slope and whether any correlation between the two is present. Measurements were performed by two independent observers using an imaging visualization software. The tibial slope was calculated on the medial and lateral side as the angle between the sagittal longitudinal axis and a Line Tangent to themedial and lateral plateau.The posterior condylar offset was calculated as the distance between the posterior femoral cortex and themost posterior point of the femoral condyle. Results: The tibial bone slope averaged 8 and 7.7, on the medial and lateral side, respectively, without significant difference between the two. The posterior offset of femoral condyles averaged 27.4 and 25.2 mm on the medial and lateral side, respectively (p = 0.001). The variation coefficient of posterior condylar offset and sagittal tibial slope was 11.5% and 38%, respectively. A significant relationship was found between the posterior condylar offset and sagittal tibial slope, but on the medial side only. Conclusions: In planning a cruciate retaining TKA, it may be helpful to take into account the posterior condylar offset and tibial slope concomitantly to achieve a satisfactory functional outcome
Victor M. Castaño - One of the best experts on this subject based on the ideXlab platform.
-
Phase change in a diffracted wave: a Cornu spiral perspective
Optics letters, 2010Co-Authors: Remy Avila, Victor M. CastañoAbstract:A simple evaluation of the phase change in a diffracted wave, in terms of the Cornu spiral, is presented to complement the well-known intensity change, which is routinely obtained for this elegant graphical construction of the Fresnel integrals. This is, to the best of our knowledge, the first presentation of this evaluation. It is shown that the phase of a wave diffracted by a slit is equal to the slope of the Line Tangent to the Cornu spiral, shifted by π/4.
Jong Woong Park - One of the best experts on this subject based on the ideXlab platform.
-
The relationship between tibial slope and meniscal insertion
Knee Surgery Sports Traumatology Arthroscopy, 2009Co-Authors: Jung Ho Park, Jong Woong ParkAbstract:Despite increasing interest in the anatomic importance of the meniscal insertion, little information is available regarding the relationship between the tibial slope and the meniscal insertion. Lateral radiographs and MRI sagittal images from 100 healthy and young patients were used in this study. Patients without deformation, meniscal pathology, or previous surgery to the ipsilateral knee were included in this study. We measured the angle between a Line Tangent to the medial and lateral tibial slope and the proximal tibial anatomical axis using a lateral radiographs. We also measured the angle between the Tangent Line to the medial and lateral tibial insertion of the meniscus and the proximal tibial anatomical axis using sagittal MRI images. The measurements were carried out twice by two observers. Inter-observer reliability ranged from 0.98 to 0.99 and intra-observer reliability ranged from 0.83 to 0.94. For each observer, the mean differences between measurements made using radiographs and MRI images were 16.4° and 16.4° on the lateral side, respectively, and 6.0° and 5.9° on the medial side, respectively. There was a statistically significant difference between measurements made using radiographs and MRI images ( p
-
The relationship between tibial slope and meniscal insertion.
Knee surgery sports traumatology arthroscopy : official journal of the ESSKA, 2009Co-Authors: Yong Seuk Lee, Jung Ho Park, Jong Woong Park, Jin Goo Kim, Hong Chul Lim, Jae Gyoon KimAbstract:Despite increasing interest in the anatomic importance of the meniscal insertion, little information is available regarding the relationship between the tibial slope and the meniscal insertion. Lateral radiographs and MRI sagittal images from 100 healthy and young patients were used in this study. Patients without deformation, meniscal pathology, or previous surgery to the ipsilateral knee were included in this study. We measured the angle between a Line Tangent to the medial and lateral tibial slope and the proximal tibial anatomical axis using a lateral radiographs. We also measured the angle between the Tangent Line to the medial and lateral tibial insertion of the meniscus and the proximal tibial anatomical axis using sagittal MRI images. The measurements were carried out twice by two observers. Inter-observer reliability ranged from 0.98 to 0.99 and intra-observer reliability ranged from 0.83 to 0.94. For each observer, the mean differences between measurements made using radiographs and MRI images were 16.4° and 16.4° on the lateral side, respectively, and 6.0° and 5.9° on the medial side, respectively. There was a statistically significant difference between measurements made using radiographs and MRI images (p < 0.001). However, the Pearson’s correlation coefficient between the measurements made using radiographs and MRI images did not show a Linear correlation. The measurements of posterior slope on lateral radiographs images and meniscal insertion on sagittal MRI images were reproducible and reliable. Differences in measurements ranged from 15° to 17° on the lateral side and from 5° to 6° on the medial side, with 95% confidence intervals. However, there was no statistical correlation between the measurements made using lateral radiographs and MRI images.