Equilibrium onions?

We demonstrate the possibility of a stable equilibrium multi-lamellar ("onion") phase in pure lamellar systems (no excess solvent) due to a sufficiently negative Gaussian curvature modulus. The onion phase is stabilized by non-linear elastic moduli coupled to a polydisperse size distribution (Apollonian packing) to allow space-filling without appreciable elastic distortion. This model is compared to experiments on copolymer-decorated lamellar surfactant systems, with reasonable qualitative agreement

Improving the performance of swift-water rescue quick release harnesses

This paper considered the effectiveness of empathic design modifications to quick release harness design. It was found that the critical element in effecting a rapid and efficient release was the tape length distal to the buckle/back-bar components. We have concluded that the length of tape pulled through the buckle and the loading of the buckle/ tri-glide are critical to ensure an effective release. Physical separation of tape and buckle mechanism when the harness is released is crucial to the effective release. We then considered the problems this may pose in multiple user situations such as ‘call out’ teams or training use and we propose that the adaptation utilised in the research harness to facilitate testing may provide a simple and low cost solution to the multiple user problem allowing easy adjustment of the harness to ensure the separation of buckle and tape on release. We conclude by outlining the design adaptations and recommendations for the training and use of the quick release harness and make recommendations for the training of QRH use

Vorticity Banding During the Lamellar-to-Onion Transition in a Lyotropic Surfactant Solution in Shear Flow

We report on the rheology of a lamellar lyotropic surfactant solution (SDS/dodecane/pentanol/water), and identify a discontinuous transition between two shear thinning regimes which correspond to the low stress lamellar phase and the more viscous shear induced multi-lamellar vesicle, or ``onion'' phase. We study in detail the flow curve, stress as a function of shear rate, during the transition region, and present evidence that the region consists of a shear banded phase where the material has macroscopically separated into bands of lamellae and onions stacked in the vorticity direction. We infer very slow and irregular transformations from lamellae to onions as the stress is increased through the two phase region, and identify distinct events consistent with the nucleation of small fractions of onions that coexist with sheared lamellae.Comment: 10 pages, 10 figure

Comparison of extraction methods for analysis of flavonoids in onions

Onions are known to contain high levels of flavonoids and a comparison of the efficiency, reproducibility and detection limits of various extraction methods has been made in order to develop fast and reliable analytical methods for analysis of flavonoids in onions. Conventional and classical methods are time- and solvent-consuming and the presence of light and oxygen during sample preparation facilitate degradation reactions. Thus, classical methods were compared with microwave (irradiation) extraction, ultrasonic liquid extraction and accelerated solvent extraction

Plasmon excitations in carbon onions: Model vs. measurements

©1998 American Institute of PhysicsNon-relativistic local dielectric response theory has proven successful in the interpretation of Electron Energy Loss data of nanometer-size isotropic particles of different geometries. In previous work, we have adapted this model to take into account anisotropy as encountered in the case of carbon onions. We have shown that this anisotropy needs to be taken into account since important deviations with respect to an isotropic model can be observed. In this contribution, we report on the first energy filtered images of carbon onions and compare intensity profiles across the spheres to our calculations

Quantum transport through single and multilayer icosahedral fullerenes

We use a tight-binding Hamiltonian and Green functions methods to calculate the quantum transmission through single-wall fullerenes and bilayered and trilayered onions of icosahedral symmetry attached to metallic leads. The electronic structure of the onion-like fullerenes takes into account the curvature and finite size of the fullerenes layers as well as the strength of the intershell interactions depending on to the number of interacting atom pairs belonging to adjacent shells. Misalignment of the symmetry axes of the concentric icosahedral shells produces breaking of the level degeneracies of the individual shells, giving rise some narrow quasi-continuum bands instead of the localized discrete peaks of the individual fullerenes. As a result, the transmission function for non symmetrical onions are rapidly varying functions of the Fermi energy. Furthermore, we found that most of the features of the transmission through the onions are due to the electronic structure of the outer shell with additional Fano-like antiresonances arising from coupling with or between the inner shells.Comment: 16 pages, 5 figur

Onion gene expression in response to ethylene and 1-MCP

Onion is regarded as a non-climacteric vegetable. In onions, however, ethylene can suppress sprouting while the ethylene binding inhibitor, 1-MCP (1- methylcyclopropene) can also suppress sprout growth yet, it is unknown how ethylene and 1-MCP elicit the same response. In this study, onions were treated with 10 μL L-1 ethylene or 1 μL L-1 1-MCP individually or in combination for 24 h at 20°C before or after curing (six weeks) at 20 or 28°C then stored at 1°C. Following curing, a subset of these same onions was stored separately under continuous air or ethylene (10 μL L- 1) at 1°C Onions treated with ethylene and 1-MCP in combination after curing for 24 h had reduced sprout growth as compared with the control 25 weeks after harvest. Sprout growth following storage beyond 25 weeks was only reduced through continuous ethylene treatment. This observation was supported by a higher proportion of down-regulated genes characterised as being involved in photosynthesis measured using a newly developed onion microarray. Physiological and biochemical data suggested that ethylene was being perceived in the presence of 1-MCP since sprout growth was reduced in onions treated with 1-MCP and ethylene applied in combination but not when applied individually. A cluster of probes representing transcripts up-regulated by 1-MCP alone but down-regulated by ethylene alone or in the presence of 1-MCP support this suggestion. Ethylene and 1-MCP both down52 regulated a probe tentatively annotated as an ethylene receptor as well as EIN3, suggesting that both treatments down-regulate the perception and signalling events of ethylene