Diffusion flame analyses

Nine classic diffusion flames, i.e., combustion systems with initially separate fuel and oxidizer, are synthesized in a search for common dimensionless parameters which may serve as indice of fire hazard. The problems examined are: planar and cylindrical Burke-Schumann; droplet burning; planar and cylindrical stagnant film; and forced, free, mixed, and stagnation point combusting boundary layers. Similarity solutions in pyrolysis regions permit identification of flame locations and quantification of excess pyrolyzate, i.e., fuel which is not consumed locally. Numerical solutions in downstream regions give explicit expressions for flame extensions in terms of the number and the B number, with the former dominating. This key parameter, the physically available oxygen-to-fuel ratio divided by the chemically required oxygen-to-fuel ratio or inverse equivalence r ratio, emerges as indicative of the fire hazard associated with flame extension. Full scale tests have shown that flame extension is related to fire spread beyond the compartment of origin. Small r means large flame. Polystyrene with r = 0.12, for example, has an order of magnitude longer flame than wood with r = 0.6. Other polymers fall between these extremes. Much progress remains to be made in the areas of flame soot, radiation, turbulence, and compartment interactions.     

风景园林之于自然重建的意义

21世纪以来,世界人口的增长要求风景园林做出积极的贡献。生态系统服务概念为我们提供了一个框架,使我们理解风景园林对人类活动有着重大意义,并且呼吁在风景园林采取可靠的措施适应紧迫的人口增长。由于在人类交互作用、生态溢流和环境体制等方面受过专门的训练,风景园林师完全胜任引领这些景观设施的发展。     

Materials Science in the Developing World: Challenges and Perspectives for Africa

“Africans believe in something that is difficult to render in English. We call it ubuntu or botho. It means the essence of being human. You know when it is there and when it is absent. It speaks about humanness, gentleness, hospitality, putting yourself out on behalf of others, being vulnerable. It embraces compassion and roughness. It recognizes that my humanity is bound up in yours, for we can only be human together” (Desmond Tutu)     

Segmentation of rough surfaces using a polarization imaging system

A polarimetric vision system yielding a roughness-segmentation-based image is described. As a general principle, the bidirectional reflectance distribution function (BRDF) of a surface is assumed to be related to its local irregularities, i.e., its roughness. This BRDF is seen as the sum of a specular and a diffuse component. In this paper we propose to introduce polarization measurements in order to estimate this roughness parameter without requiring any assumption for the model of the diffuse component, nor is diffuse-specular separation required. Moreover, with the proposed method, the refractive indices of the observed objects are estimated at each pixel. Examples are given for quality control applications.     

On flow properties,fibre distribution,fibre orientation and flexural behaviour of FRC

For improving the mechanical properties of fibre reinforced concrete one can either increase the fibre content, use hybrid fibre systems, or one can attempt to align fibres in the direction of stress. In this paper, it is attempted to use the flow-properties of the fresh (self-compacting) concrete to change the fibre distribution and orientation. Using a single mixture of fibre reinforced concrete, containing 3% of 30 mm long straight steel fibres, the fibre distribution and orientation was determined in three different parts of a ‘U-shaped specimen’ where the concrete could flow in three different directions. The fibre distribution and orientation was determined from a CT-scan. Flexural tests show that the mechanical behaviour depends on the fibre distribution and orientation, which can be affected by changing the viscosity of the fresh mixture.     

Strain control and spontaneous phase ordering in vertical nanocomposite heteroepitaxial thin films

Two-phase, vertical nanocomposite heteroepitaxial films hold great promise for (multi)functional device applications. In order to achieve practical devices, a number of hurdles need to be overcome, including the creation of ordered structures (and their formation on a large scale), achieving different combinations of materials and control of strain coupling between the phases. Here we demonstrate major advances on all these fronts: remarkable spontaneously ordered structures were produced in newly predicted compositions, vertical strain was proven to dominate the strain state in films above 20 nm thickness and strain manipulation was demonstrated by selection of phases with the appropriate elastic moduli. The work opens up a new avenue for strain control in relatively thick films and also promises new forms of ordered nanostructures for multifunctional applications.     

Ionic effects on the equilibrium dynamics of DNA confined in nanoslits

The ionic effects on the dynamics and conformation of DNA in silt-like confinement are investigated. Confined lambda-DNA is considered as a model polyelectrolyte, and its longest relaxation time, diffusivity, and size are measured at a physiological ionic strength between 1.7-170 mM. DNA properties change drastically in response to the varying ionic environment, and these changes can be explained by blob theory with an electrostatically mediated effective diameter and persistence length. In the ionic range we investigate, the effective diameter of DNA that represents the electrostatic repulsion between remote segments is found to be the main driving force for the observed change in DNA properties. Our results are useful for understanding the manipulation of biomolecules in nanofluidic devices.     

Detection of single photoluminescent diamond nanoparticles in cells and study of the internalization pathway

Diamond nanoparticles are promising photoluminescent probes for tracking intracellular processes, due to embedded, perfectly photostable color centers. In this work, the spontaneous internalization of such nanoparticles (diameter 25 nm) in HeLa cancer cells is investigated by confocal microscopy and time-resolved techniques. Nanoparticles are observed inside the cell cytoplasm at the single-particle and single-color-center level, assessed by time-correlation intensity measurements. Improvement of the nanoparticle signal-to-noise ratio inside the cell is achieved using a pulsed-excitation laser and time-resolved detection taking advantage of the long radiative lifetime of the color-center excited state as compared to cell autofluorescence. The internalization pathways are also investigated, with endosomal marking and colocalization analyses. The low colocalization ratio observed proves that nanodiamonds are not trapped in endosomes, a promising result in prospect of drug delivery by these nanoparticles. Low cytotoxicity of these nanoparticles in this cell line is also shown.     

Discovery of new hexagonal supramolecular nanostructures formed by squalenoylation of an anticancer nucleoside analogue

In this study, the dynamically folded conformation of squalene (SQ) is taken advantage of to link this natural compound to the anticancer nucleoside analogue gemcitabine (gem) in order to achieve the spontaneous formation of nanoassemblies (SQgem) in water. Cryogenic transmission electron microscopy examination reveals particles (104 nm) with a hexagonal or multifaceted shape that display an internal structure made of reticular planes, each particle being surrounded by an external shell. X-ray diffraction evidences the hexagonal molecular packing of SQgem, resulting from the stacking of direct or inverse cylinders. The respective volumes of the gem and SQ molecules as well as molecular modeling of SQgem suggest the stacking of inverse hexagonal phases, in which the central aqueous core, consisting of water and gem molecules, is surrounded by SQ moieties. These SQgem nanoassemblies also exhibit impressively greater anticancer activity than gem against a solid subcutaneously grafted tumor, following intravenous administration. To our knowledge, this is the first demonstration of hexagonal phase organization with a SQ derivative.     

Retrospective reports of parental physical affection and parenting style: A study of Finnish twins.

Individual differences in parenting behaviors are due, in part, to genetic factors. In the present study, the authors sought to determine whether the degree of genetic influence varied according to the type of parental behavior under consideration. A population-based sample of 2,334 pairs of Finnish twins provided ratings on the physical affection, control, abusiveness, and indifference shown by their father and mother during childhood. Genetic influences, shared environmental influences, and nonshared environmental influences accounted for a small-to-medium proportion (17%-30%), a small-to-large proportion (22%-44%), and a medium-to-large proportion (37%-55%) of the variance in each parenting measure, respectively. There were no significant differences in effect sizes for mothers and fathers or across the 4 types of parental behavior. The genetic results may reflect characteristic styles with which parents respond to genetically influenced behaviors of individuals (gene-environment correlations) or individual perceptions of this relationship (gene-person correlation processes). The findings have implications for intervention and prevention work with families and for interpretation of evidence for interactions between genes and parenting behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)