23,551 research outputs found
Development and application of a self-referencing glucose microsensor for the measurement of glucose consumption by pancreatic ?-cells
Glucose gradients generated by an artificial source and ?-cells were measured using an enzyme-based glucose microsensor, 8-?m tip diameter, as a self-referencing electrode. The technique is based on a difference measurement between two locations in a gradient and thus allows us to obtain real-time flux values with minimal impact of sensor drift or noise. Flux values were derived by incorporation of the measured differential current into Fick's first equation. In an artificial glucose gradient, a flux detection limit of 8.2 ± 0.4 pmol·cm-2·s-1 (mean ± SEM, n = 7) with a sensor sensitivity of 7.0 ± 0.4 pA/mM (mean ± SEM, n = 16) was demonstrated. Under biological conditions, the glucose sensor showed no oxygen dependence with 5 mM glucose in the bulk medium. The addition of catalase to the bulk medium was shown to ameliorate surface-dependent flux distortion close to specimens, suggesting an underlying local accumulation of hydrogen peroxide. Glucose flux from ?-cell clusters, measured in the presence of 5 mM glucose, was 61.7 ± 9.5 fmol·nL-1·s-1 (mean ± SEM, n = 9) and could be pharmacologically modulated. Glucose consumption in response to FCCP (1 ?M) transiently increased, subsequently decreasing to below basal by 93 ± 16 and 56 ± 6%, respectively (mean ± SEM, n = 5). Consumption was decreased after the application of 10 ?M rotenone by 74 ± 5% (mean ± SEM, n = 4). These results demonstrate that an enzyme-based amperometric microsensor can be applied in the self-referencing mode. Further, in obtaining glucose flux measurements from small clusters of cells, these are the first recordings of the real-time dynamic of glucose movements in a biological microenvironment. <br/
Electronic structures of doped anatase : (M=Co, Mn, Fe, Ni)
We have investigated electronic structures of a room temperature diluted
magnetic semiconductor : Co-doped anatase . We have obtained the
half-metallic ground state in the local-spin-density approximation(LSDA) but
the insulating ground state in the LSDA++SO incorporating the spin-orbit
interaction. In the stoichiometric case, the low spin state of Co is realized
with the substantially large orbital moment. However, in the presence of oxygen
vacancies near Co, the spin state of Co becomes intermediate. The
ferromagnetisms in the metallic and insulating phases are accounted for by the
double-exchange-like and the superexchange mechanism, respectively. Further,
the magnetic ground states are obtained for Mn and Fe doped ,
while the paramagnetic ground state for Ni-doped .Comment: 5 pages, 4 figure
Anomalous double peak structure in Nb/Ni superconductor/ferromagnet tunneling DOS
We have experimentally investigated the density of states (DOS) in Nb/Ni
(S/F) bilayers as a function of Ni thickness, . Our thinnest samples show
the usual DOS peak at , whereas intermediate-thickness samples
have an anomalous ``double-peak'' structure. For thicker samples ( nm), we see an ``inverted'' DOS which has previously only been reported in
superconductor/weak-ferromagnet structures. We analyze the data using the
self-consistent non-linear Usadel equation and find that we are able to
quantitatively fit the features at if we include a large amount
of spin-orbit scattering in the model. Interestingly, we are unable to
reproduce the sub-gap structure through the addition of any parameter(s).
Therefore, the observed anomalous sub-gap structure represents new physics
beyond that contained in the present Usadel theory.Comment: 4 pages, 3 figure
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Social Enterprise Growth by Design: Using design to incubate and accelerate social enterprises
Purpose:
The paper aims to explore the roles and impact of design in incubating and accelerating social enterprises. It aims to understand design’s influence on social enterprise ecosystems and in improving outcomes for social enterprises.
Design/methodology/approach:
The study used an exploratory, qualitative approach, using case studies and interviews. The comparative case-study methodology was applied to evaluate the influence of design on the development of social enterprises in the UK and South Korea and identify critical issues in their utilisation of design. Empirical data included: in-depth case studies of design utilisation practices (UK = 6; South Korea = 15) and design applications (UK = 2; South Korea = 2) for the growth of social enterprise and its ecosystem; 27 social enterprise/design experts (UK = 17; South Korea = 10); and 22 social enterprises (UK = 12; South Korea = 10). Content and thematic analysis were used to synthesise the findings.
Findings:
Findings demonstrate the differing influences of design on social enterprise, from improving products/services and business models to enhancing social enterprise ecosystem support and networks. Future directions are suggested for applying design for social enterprise growth, business stage development and systematising interactions between the social enterprise and design sectors.
Research limitations/implications:
The research is based on case studies from only two countries. Further, the adoption of working definitions of social enterprise in the countries may result in the research underestimating the heterogeneity of social enterprise.
Practical implications:
The findings contribute to optimising efficient ecosystem development to improve social enterprise competitiveness and innovation.
Originality/value:
This paper establishes a research foundation on design for social enterprise, offering theoretical and practical insights into its impact on growth
Orientational Melting in Carbon Nanotube Ropes
Using Monte Carlo simulations, we investigate the possibility of an
orientational melting transition within a "rope" of (10,10) carbon nanotubes.
When twisting nanotubes bundle up during the synthesis, orientational
dislocations or twistons arise from the competition between the anisotropic
inter-tube interactions, which tend to align neighboring tubes, and the torsion
rigidity that tends to keep individual tubes straight. We map the energetics of
a rope containing twistons onto a lattice gas model and find that the onset of
a free "diffusion" of twistons, corresponding to orientational melting, occurs
at T_OM > 160 K.Comment: 4 page LaTeX file with 3 figures (10 PostScript files
Collimating lenses from non-Euclidean transformation optics
Based on the non-Euclidean transformation optics, we design a thin
metamaterial lens that can achieve wide-beam radiation by embedding a simple
source (a point source in three-dimensional case or a line current source in
two-dimensional case). The scheme is performed on a layer-by-layer geometry to
convert curved surfaces in virtual space to flat sheets, which pile up and form
the entire lens in physical space. Compared to previous designs, the lens has
no extreme material parameters. Simulation results confirm its functionality.Comment: 12 pages, 6 figure
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