Relationship among Corneal Biomechanics, Refractive Error, and Axial Length

Purpose: To evaluate the relationship between different ocular and corneal biomechanical parameters in emmetropic and ametropic healthy white children. Methods: This study included 293 eyes of 293 healthy Spanish children (135 boys and 158 girls), ranging in age from 6 to 17 years. Subjects were divided according to the refractive error: control (emmetropia, 99 children), myopia (100 children), and hyperopia (94 children) groups. In all cases, corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated with the Ocular Response Analyzer system. Axial length (AL) and mean corneal power were also measured by partial coherence interferometry (IOLMaster), and central corneal thickness (CCT) and anterior chamber depth were measured by anterior segment optical coherence tomography (Visante). Results: Mean (±SD) CH and CRF were 12.12 (±1.71) and 12.30 (±1.89) mm Hg, respectively. Mean (±SD) CCT was 542.68 (±37.20) μm and mean (±SD) spherical equivalent was +0.14 (±3.41) diopters. A positive correlation was found between CH and CRF (p < 0.001), and both correlated as well with CCT (p < 0.0001). Corneal resistance factor was found to decrease with increasing age (p = 0.01). Lower levels of CH were associated with longer AL and more myopia (p < 0.001 and p = 0.001, respectively). Higher values of CH were associated with increasing hyperopia. Significant differences in CH were found between emmetropic and myopic groups (p < 0.001) and between myopic and hyperopic groups (p = 0.011). There were also significant differences in CRF between emmetropic and myopic groups (p = 0.02). Multiple linear regression analysis showed that lower CH and CRF significantly associated with thinner CCT, longer AL, and flatter corneal curvature. Conclusions: The Ocular Response Analyzer corneal biomechanical properties seem to be compromised in myopia from an early age, especially in high myopia.

Wind Shear, Gust, and Yaw-Induced Dynamic Stall on Wind-Turbine Blades

This study examined the effect of a spanwise angle of attack gradient on the growth and stability of a dynamic stall vortex in a rotating system. It was found that a spanwise angle of attack gradient induces a corresponding spanwise vorticity gradient, which, in combination with spanwise flow, results in a redistribution of circulation along the blade. Specifically, when modelling the angle of attack gradient experienced by a wind turbine at the 30% span position during a gust event, the spanwise vorticity gradient was aligned such that circulation was transported from areas of high circulation to areas of low circulation, increasing the local dynamic stall vortex growth rate, which corresponds to an increase in the lift coefficient, and a decrease in the local vortex stability at this point. Reversing the relative alignment of the spanwise vorticity gradient and spanwise flow results in circulation transport from areas of low circulation generation to areas of high circulation generation, acting to reduce local circulation and stabilise the vortex. This circulation redistribution behaviour describes a mechanism by which the fluctuating loads on a wind turbine are magnified, which is detrimental to turbine lifetime and performance. Therefore, an understanding of this phenomenon has the potential to facilitate optimised wind turbine design.

Avaliação da composição corporal e do estado nutricional em doentes com neoplasias gastrointestinais : bioimpedância elétrica e tomografia axial computorizada, que correlação?

Tese de mestrado, Nutrição Clínica, Faculdade de Medicina, Universidade de Lisboa, 2015

Switching Axial Progenitors from Producing Trunk to Tail Tissues in Vertebrate Embryos

The vertebrate body is made by progressive addition of new tissue from progenitors at the posterior embryonic end. Axial extension involves different mechanisms that produce internal organs in the trunk but not in the tail. We show that Gdf11 signaling is a major coordinator of the trunk-to-tail transition. Without Gdf11 signaling, the switch from trunk to tail is significantly delayed, and its premature activation brings the hindlimbs and cloaca next to the forelimbs, leaving extremely short trunks. Gdf11 activity includes activation of Isl1 to promote formation of the hindlimbs and cloaca-associated mesoderm as the most posterior derivatives of lateral mesoderm progenitors. Gdf11 also coordinates reallocation of bipotent neuromesodermal progenitors from the anterior primitive streak to the tail bud, in part by reducing the retinoic acid available to the progenitors. Our findings provide a perspective to understand the evolution of the vertebrate body plan.

Controlling Hox gene expression and activity to build the vertebrate axial skeleton

It has long been known that Hox genes are central players in patterning the vertebrate axial skeleton. Extensive genetic studies in the mouse have revealed that the combinatorial activity of Hox genes along the anterior-posterior body axis specifies different vertebral identities. In addition, Hox genes were instrumental for the evolutionary diversification of the vertebrate body plan. In this review, we focus on fundamental questions regarding the intricate mechanisms controlling Hox gene activity. In particular, we discuss the functional relevance of the precise timing of Hox gene activation in the embryo. Moreover, we provide insight into the epigenetic regulatory mechanisms that are likely to control this process and are responsible for the maintenance of spatially restricted Hox expression domains throughout embryonic development. We also analyze how specific features of each Hox protein may contribute to the functional diversity of Hox family. Altogether, the work reviewed here further supports the notion that the Hox program is far more complex than initially assumed. Exciting new findings will surely emerge in the years ahead.

Compartment-dependent activities of Wnt3a/β-catenin signaling during vertebrate axial extension

Extension of the vertebrate body results from the concerted activity of many signals in the posterior embryonic end. Among them, Wnt3a has been shown to play relevant roles in the regulation of axial progenitor activity, mesoderm formation and somitogenesis. However, its impact on axial growth remains to be fully understood. Using a transgenic approach in the mouse, we found that the effect of Wnt3a signaling varies depending on the target tissue. High levels of Wnt3a in the epiblast prevented formation of neural tissues, but did not impair axial progenitors from producing different mesodermal lineages. These mesodermal tissues maintained a remarkable degree of organization, even within a severely malformed embryo. However, from the cells that failed to take a neural fate, only those that left the epithelial layer of the epiblast activated a mesodermal program. The remaining tissue accumulated as a folded epithelium that kept some epiblast-like characteristics. Together with previously published observations, our results suggest a dose-dependent role for Wnt3a in regulating the balance between renewal and selection of differentiation fates of axial progenitors in the epiblast. In the paraxial mesoderm, appropriate regulation of Wnt/β-catenin signaling was required not only for somitogenesis, but also for providing proper anterior-posterior polarity to the somites. Both processes seem to rely on mechanisms with different requirements for feedback modulation of Wnt/β-catenin signaling, once segmentation occurred in the presence of high levels of Wnt3a in the presomitic mesoderm, but not after permanent expression of a constitutively active form of β-catenin. Together, our findings suggest that Wnt3a/β-catenin signaling plays sequential roles during posterior extension, which are strongly dependent on the target tissue. This provides an additional example of how much the functional output of signaling systems depends on the competence of the responding cells.

Ceramic applications in turbine engines.

Energy Department, Office of Vehicle and Engine Research and Development, Washington, D.C.

Preliminary test on axial spindle expansion of nuber 739 Ex-Cell-O numerical tape control machine /

"U.S. Atomic Energy Commission Contract AT(29-1)-1106."

A theory for the effect of mean stress on fatigue of metals under combined torsion and axial load or bending.

"Department of Army Project no. 5B99-01-004, Ordnance R and D Project no. TB2-0001, Office of Ordnance Research Project no. 1348, Contract no. DA-19-020-ORD-3250."

Boiler and turbine room instruments; serial report of the Prime Movers Committee (1925-1926)

Mode of access: Internet.

Axial tension and bending interaction curves for members loaded inelastically,

Mode of access: Internet.

Research on rotating stall in axial flow compressors.

"January 1959."

Wind turbine generator system, Block Island, Rhode Island : final environmental impact statement /

"DOE/EIS-0006; UC 11, 13, 60."