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Current Limits (current + limit)

Distribution by Scientific Domains

Chemistry	40%

Selected Abstracts

Integrated on-chip derivatization and electrophoresis for the rapid analysis of biogenic amines

ELECTROPHORESIS, Issue 14 2004
Nigel P. Beard
Abstract We demonstrate the monolithic integration of a chemical reactor with a capillary electrophoresis device for the rapid and sensitive analysis of biogenic amines. Fluorescein isothiocyanate (FITC) is widely employed for the analysis of amino-group containing analytes. However, the slow reaction kinetics hinders the use of this dye for on-chip labeling applications. Other alternatives are available such as o -phthaldehyde (OPA), however, the inferior photophysical properties and the UV ,max present difficulties when using common excitation sources leading to a disparity in sensitivity. Consequently, we present for the first time the use of dichlorotriazine fluorescein (DTAF) as a superior in situ derivatizing agent for biogenic amines in microfluidic devices. The developed microdevice employs both hydrodynamic and electroosmotic flow, facilitating the creation of a polymeric microchip to perform both precolumn derivatization and electrophoretic analysis. The favorable photophysical properties of the DTAF and its fast reaction kinetics provide detection limits down to 1 nM and total analysis times (including on-chip mixing and reaction) of <60 s. The detection limits are two orders of magnitude lower than current limits obtained with both FITC and OPA. The optimized microdevice is also employed to probe biogenic amines in real samples. [source]

Ambivalence, Contradiction, and Symbiosis: Carers' and Mental Health Users' Rights

LAW & POLICY, Issue 4 2007
VICTORIA YEATES
This article explores the emergence of separate rights for carers and psychiatric service users. Although political rhetoric and policy documents largely assume symbiosis between carer and cared-for person, increasingly the law reflects that their rights and interests may conflict and operate in opposition one to another. This article examines the social and policy factors that lie behind these developments and disentangles some of the ambivalences, contradictions, and symbioses that characterize this area of law. While service users' rights in relation to decisions about their care have emerged from the shadow of family rights, carers' rights to community support services have emerged as an adjunct to service users' rights. The article explores the development of the rights paradigm in promoting the welfare of mentally disordered people and their carer, and the current limits of separation between their respective entitlements. [source]

Evaluation of ball and disc wear scar data in the HFRR lubricity test

LUBRICATION SCIENCE, Issue 1 2008
Gerhard Knothe
Abstract The high-frequency reciprocating rig (HFRR) lubricity tester has become a widespread method for determining the lubricity of diesel fuels. The test is a ball-on-disc method, in which a steel ball scrapes over a steel disc immersed in the liquid to be tested. According to standards, the wear scar generated on the ball, in the form of the average of the x - and y -axes, is used for evaluating the lubricity of the sample. Generally, the smaller the wear scar, the greater the lubricity of the sample. However, a wear scar is also generated on the disc. The size of the wear scar on the disc also depends on the lubricity of the sample. In this work, the wear scar data of the balls and discs of 230 samples related to the testing of biodiesel and related compounds with petrodiesel were evaluated. Data comparisons for all wear scar combinations correlated well by linear regression. Although correlations are slightly better when using only ball wear scar data (r2 > 0.99), other wear scar data, including those generated on the disc, appear just as useable (r2 , 0.97,0.99) for evaluating lubricity by the HFRR test. The wear scars on the disc have the advantage of being more easily measurable and recognisable under the microscope, especially if the wear scars are small. Limits for all wear scar values corresponding to current limits for average ball wear scar data in standards are presented. Published in 2007 by John Wiley & Sons, Ltd. [source]

The minimum crystal size needed for a complete diffraction data set

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2010
James M. Holton
In this work, classic intensity formulae were united with an empirical spot-fading model in order to calculate the diameter of a spherical crystal that will scatter the required number of photons per spot at a desired resolution over the radiation-damage-limited lifetime. The influences of molecular weight, solvent content, Wilson B factor, X-ray wavelength and attenuation on scattering power and dose were all included. Taking the net photon count in a spot as the only source of noise, a complete data set with a signal-to-noise ratio of 2 at 2,Å resolution was predicted to be attainable from a perfect lysozyme crystal sphere 1.2,µm in diameter and two different models of photoelectron escape reduced this to 0.5 or 0.34,µm. These represent 15-fold to 700-fold less scattering power than the smallest experimentally determined crystal size to date, but the gap was shown to be consistent with the background scattering level of the relevant experiment. These results suggest that reduction of background photons and diffraction spot size on the detector are the principal paths to improving crystallographic data quality beyond current limits. [source]

Photoconduction in Amorphous Organic Solids

CHEMPHYSCHEM, Issue 5 2008
Dirk Hertel Dr.
Abstract Herein, we focus on the principles of photoconduction in random semiconductors,the key processes being optical generation of charge carriers and their subsequent transport. This is not an overview of the current work in this area, but rather a highlight of elementary processes, their involvement in modern devices and a summary of recent developments and achievements. Experimental results and models are discussed briefly to visualize the mechanism of optical charge generation in pure and doped organic solids. We show current limits of models based on the Onsager theory of charge generation. After the introduction of experimental techniques to characterize charge transport, the hopping concept for transport in organic semiconductors is outlined. The peculiarities of the transport of excitons and charges in disorderd organic semiconductors are highlighted. Finally, a short discussion of ultrafast transport and single chain transport completes the review. [source]