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281.
282.
Carol D. Curtis Reema B. Davis Kyle G. Ingram Courtney T. Griffin 《Cellular and molecular life sciences : CMLS》2012,69(23):3921-3931
Vascular development is a dynamic process that relies on the coordinated expression of numerous genes, but the factors that regulate gene expression during blood vessel development are not well defined. ATP-dependent chromatin-remodeling complexes are gaining attention for their specific temporal and spatial effects on gene expression during vascular development. Genetic mutations in chromatin-remodeling complex subunits are revealing roles for the complexes in vascular signaling pathways at discrete developmental time points. Phenotypic analysis of these models at various stages of vascular development will continue to expand our understanding of how chromatin remodeling impacts new blood vessel growth. Such research could also provide novel therapeutic targets for the treatment of vascular pathologies. 相似文献
283.
Liquid marbles. 总被引:5,自引:0,他引:5
The transport of a small amount of liquid on a solid is not a simple process, owing to the nature of the contact between the two phases. Setting a liquid droplet in motion requires non-negligible forces (because the contact-angle hysteresis generates a force opposing the motion), and often results in the deposition of liquid behind the drop. Different methods of levitation-electrostatic, electromagnetic, acoustic, or even simpler aerodynamic techniques-have been proposed to avoid this wetting problem, but all have proved to be rather cumbersome. Here we propose a simple alternative, which consists of encapsulating an aqueous liquid droplet with a hydrophobic powder. The resulting 'liquid marbles' are found to behave like a soft solid, and show dramatically reduced adhesion to a solid surface. As a result, motion can be generated using gravitational, electrical and magnetic fields. Moreover, because the viscous friction associated with motion is very small, we can achieve quick displacements of the droplets without any leaks. All of these features are of potential benefit in microfluidic applications, and also permit the study of a drop in a non-wetting situation-an issue of renewed interest following the recent achievement of super-hydrophobic substrates. 相似文献
284.
On-chip natural assembly of silicon photonic bandgap crystals. 总被引:20,自引:0,他引:20
Photonic bandgap crystals can reflect light for any direction of propagation in specific wavelength ranges. This property, which can be used to confine, manipulate and guide photons, should allow the creation of all-optical integrated circuits. To achieve this goal, conventional semiconductor nanofabrication techniques have been adapted to make photonic crystals. A potentially simpler and cheaper approach for creating three-dimensional periodic structures is the natural assembly of colloidal microspheres. However, this approach yields irregular, polycrystalline photonic crystals that are difficult to incorporate into a device. More importantly, it leads to many structural defects that can destroy the photonic bandgap. Here we show that by assembling a thin layer of colloidal spheres on a silicon substrate, we can obtain planar, single-crystalline silicon photonic crystals that have defect densities sufficiently low that the bandgap survives. As expected from theory, we observe unity reflectance in two crystalline directions of our photonic crystals around a wavelength of 1.3 micrometres. We also show that additional fabrication steps, intentional doping and patterning, can be performed, so demonstrating the potential for specific device applications. 相似文献
285.
This article studies Man and Tiao's (2006) low‐order autoregressive fractionally integrated moving‐average (ARFIMA) approximation to Tsai and Chan's (2005b) limiting aggregate structure of the long‐memory process. In matching the autocorrelations, we demonstrate that the approximation works well, especially for larger d values. In computing autocorrelations over long lags for larger d value, using the exact formula one might encounter numerical problems. The use of the ARFIMA(0, d, d?1) model provides a useful alternative to compute the autocorrelations as a really close approximation. In forecasting future aggregates, we demonstrate the close performance of using the ARFIMA(0, d, d?1) model and the exact aggregate structure. In practice, this provides a justification for the use of a low‐order ARFIMA model in predicting future aggregates of long‐memory process. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
286.
287.
D Cyranoski 《Nature》2001,414(6862):381-382
288.
Immune recognition. A new receptor for beta-glucans. 总被引:26,自引:0,他引:26
The carbohydrate polymers known as beta-1,3-d-glucans exert potent effects on the immune system - stimulating antitumour and antimicrobial activity, for example - by binding to receptors on macrophages and other white blood cells and activating them. Although beta-glucans are known to bind to receptors, such as complement receptor 3 (ref. 1), there is evidence that another beta-glucan receptor is present on macrophages. Here we identify this unknown receptor as dectin-1 (ref. 2), a finding that provides new insights into the innate immune recognition of beta-glucans. 相似文献
289.
290.
J. D. R. de Raadt 《Systemic Practice and Action Research》2011,24(6):509-521
Starting from the crisis in our communities—research has indicated it to be widely spread—the author explores the scientific
tradition preceding the rise of modernism in order to draw out a more humane way of thinking that may help our contemporary
societies. He discerns between two types of Renaissance humanism, one characterised by its cleverness, the other by its compassion
and desire to restore dignity to the lives of people struggling to escape the clutches of medievalism. The father of the latter
is Erasmus of Rotterdam and we follow the development of his conception of a social humanism as it branches out, through the
work of his successors, into every scientific discipline, both natural and human. These disciplines are united by an embracing
systemic idea of philosophy that unites the mind with the heart and which Erasmus called “Philosophia Christi”. We examine
the two main pillars upon which this philosophy is built, love for our neighbour and education as the only legitimate instrument
to change society, and the extraordinary impact it had on science and on communities living in the seventeenth century. We
contrast this with the idea of power, the chosen instrument of modernity to transform society, and trace some of its tragic
outcomes. We conclude by discussing the incorporation of an Erasmian type of social humanism into systems education and the
future development of such programmes. 相似文献