The Experts below are selected from a list of 18354 Experts worldwide ranked by ideXlab platform
D.m. Wilson - One of the best experts on this subject based on the ideXlab platform.
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Pulse-based interface circuits for SPR sensing systems [Analyte Concentration measurement]
2005 IEEE International Symposium on Circuits and Systems, 2005Co-Authors: L.e. Hansen, M.m.w. Johnston, D.m. WilsonAbstract:This paper presents a means for reducing the impact of dark current, photodetector mismatch (fixed pattern noise), and the background medium on the signals generated by a surface plasmon resonance (SPR) sensing system for determining the Concentration of targeted Analytes in solution. Results for each circuit component (simulated and experimental) correlate well, with a maximum error of 3%, 7% and 12% in basic behavior (between simulated and actual results) for the dark current reduction, background medium compensation, and weighted sum circuits at relevant operating points, respectively. System level results on SPR signals also demonstrate the usefulness of these circuits for system-on-chip style signal processing. The chip produces a single output that indicates the refractive index (and resulting Analyte Concentration) of an SPR probe, independent of fluctuations in the background medium.
Graham Ross Dallas Jones - One of the best experts on this subject based on the ideXlab platform.
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Critical difference calculations revised: inclusion of variation in standard deviation with Analyte Concentration.
Annals of clinical biochemistry, 2009Co-Authors: Graham Ross Dallas JonesAbstract:The critical difference (CD), the smallest difference between sequential laboratory results which is associated with a true change in the patient, is commonly calculated by assuming the same standard deviation (SD) for the initial and subsequent measurements. The calculation of the CD is re-examined without making this assumption. A formula for CD is developed, which specifies that even with the assumption of constant coefficient of variations (CV) at the two measurement Concentrations used in the calculation, there will be different SDs due to different Concentrations. The effect of removing the assumption of constant SD is to increase the CD for rises in Analyte Concentration and to decrease the CD for falls in Concentration. These effects are caused by increased SD for the second measurement compared with the first when the second measurement is higher, and the reverse when the second is lower. Replacing the usual assumption of similar total result SD for both measurements included in the CD calculation with a calculation of the SD at both Analyte Concentrations leads to an increase in the magnitude of the CD for rises in Analyte Concentration and a decrease for falls in Analyte Concentration. This change is proposed for all forms of CD calculations.
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critical difference calculations revised inclusion of variation in standard deviation with Analyte Concentration
Annals of Clinical Biochemistry, 2009Co-Authors: Graham Ross Dallas JonesAbstract:BackgroundThe critical difference (CD), the smallest difference between sequential laboratory results which is associated with a true change in the patient, is commonly calculated by assuming the same standard deviation (SD) for the initial and subsequent measurements. The calculation of the CD is re-examined without making this assumption.MethodsA formula for CD is developed, which specifies that even with the assumption of constant coefficient of variations (CV) at the two measurement Concentrations used in the calculation, there will be different SDs due to different Concentrations.ResultsThe effect of removing the assumption of constant SD is to increase the CD for rises in Analyte Concentration and to decrease the CD for falls in Concentration. These effects are caused by increased SD for the second measurement compared with the first when the second measurement is higher, and the reverse when the second is lower.ConclusionsReplacing the usual assumption of similar total result SD for both measuremen...
L.e. Hansen - One of the best experts on this subject based on the ideXlab platform.
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Pulse-based interface circuits for SPR sensing systems [Analyte Concentration measurement]
2005 IEEE International Symposium on Circuits and Systems, 2005Co-Authors: L.e. Hansen, M.m.w. Johnston, D.m. WilsonAbstract:This paper presents a means for reducing the impact of dark current, photodetector mismatch (fixed pattern noise), and the background medium on the signals generated by a surface plasmon resonance (SPR) sensing system for determining the Concentration of targeted Analytes in solution. Results for each circuit component (simulated and experimental) correlate well, with a maximum error of 3%, 7% and 12% in basic behavior (between simulated and actual results) for the dark current reduction, background medium compensation, and weighted sum circuits at relevant operating points, respectively. System level results on SPR signals also demonstrate the usefulness of these circuits for system-on-chip style signal processing. The chip produces a single output that indicates the refractive index (and resulting Analyte Concentration) of an SPR probe, independent of fluctuations in the background medium.
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ISCAS (2) - Pulse-based interface circuits for SPR sensing systems [Analyte Concentration measurement]
2005 IEEE International Symposium on Circuits and Systems, 2005Co-Authors: L.e. Hansen, M.m.w. Johnston, Denise WilsonAbstract:This paper presents a means for reducing the impact of dark current, photodetector mismatch (fixed pattern noise), and the background medium on the signals generated by a surface plasmon resonance (SPR) sensing system for determining the Concentration of targeted Analytes in solution. Results for each circuit component (simulated and experimental) correlate well, with a maximum error of 3%, 7% and 12% in basic behavior (between simulated and actual results) for the dark current reduction, background medium compensation, and weighted sum circuits at relevant operating points, respectively. System level results on SPR signals also demonstrate the usefulness of these circuits for system-on-chip style signal processing. The chip produces a single output that indicates the refractive index (and resulting Analyte Concentration) of an SPR probe, independent of fluctuations in the background medium.
T M Pappenfus - One of the best experts on this subject based on the ideXlab platform.
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electrically stretched capacitive membranes for stiffness sensing and Analyte Concentration measurement
Sensors and Actuators B-chemical, 2008Co-Authors: Shyam Sivaramakrishnan, Rajesh Rajamani, T M PappenfusAbstract:A novel method for stiffness sensing is developed using an electret capacitive sensor. The electret membrane is coated with a recognition layer that responds with a change in its stiffness/elasticity in the presence of a target Analyte. Since the electret membrane is stretched by electrostatic pulling towards a metallic base plate, a change in stiffness of the composite membrane results in deflection of the membrane. This deflection is measured as a change in capacitance of the sensor. The sensitivity of the sensor to stiffness changes depends on the strength of the preset electric field. The developed sensor operates in a quasi-static mode and eliminates the need for resonant monitoring. The sealed capacitive sensor is ideal for monitoring Analytes in both gas and liquid environments. The final sensor package with the capacitance measurement circuitry has a low power consumption (<30 mW). A proof-of-concept carbon dioxide gas Concentration sensor is developed by coating the electret sensor with a single-walled nanotube film whose stiffness changes in the presence of carbon dioxide. Experimental results prove the viability of the sensing technique.
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Electrically stretched capacitive membranes for stiffness sensing and Analyte Concentration measurement
Sensors and Actuators B-chemical, 2008Co-Authors: Shyam Sivaramakrishnan, Rajesh Rajamani, T M PappenfusAbstract:A novel method for stiffness sensing is developed using an electret capacitive sensor. The electret membrane is coated with a recognition layer that responds with a change in its stiffness/elasticity in the presence of a target Analyte. Since the electret membrane is stretched by electrostatic pulling towards a metallic base plate, a change in stiffness of the composite membrane results in deflection of the membrane. This deflection is measured as a change in capacitance of the sensor. The sensitivity of the sensor to stiffness changes depends on the strength of the preset electric field. The developed sensor operates in a quasi-static mode and eliminates the need for resonant monitoring. The sealed capacitive sensor is ideal for monitoring Analytes in both gas and liquid environments. The final sensor package with the capacitance measurement circuitry has a low power consumption (
Nils Calander - One of the best experts on this subject based on the ideXlab platform.
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Analyte Concentration at the tip of a nanopipette
Analytical Chemistry, 2009Co-Authors: Nils CalanderAbstract:Concentration of molecules within the tips of nanopipettes when applying a DC voltage is herein investigated using finite-element simulations. The ion Concentrations and fluxes due to diffusion, electro-migration, and electro-osmotic flow, and the electric potential are determined by the simultaneous solution of the Nernst−Planck, Poisson, and Navier−Stokes equations within the water solution containing sodium and chloride ions and negatively charged molecules. The electric potential within the pipette glass wall is at the same time determined by the Poisson equation together with appropriate boundary conditions and accounts for a field effect through the wall. Fixed negative surface charge on both the internal and external glass surfaces of the nanopipette is included together with the field effect through the glass wall to account for the electric double layer and the electro-osmosis. The inclusion of the field effect through the pipette wall is new compared to previous modeling of similar structures an...
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Analyte Concentration at the tip of a nanopipette
Analytical Chemistry, 2009Co-Authors: Nils CalanderAbstract:Concentration of molecules within the tips of nanopipettes when applying a DC voltage is herein investigated using finite-element simulations. The ion Concentrations and fluxes due to diffusion, electro-migration, and electro-osmotic flow, and the electric potential are determined by the simultaneous solution of the Nernst-Planck, Poisson, and Navier-Stokes equations within the water solution containing sodium and chloride ions and negatively charged molecules. The electric potential within the pipette glass wall is at the same time determined by the Poisson equation together with appropriate boundary conditions and accounts for a field effect through the wall. Fixed negative surface charge on both the internal and external glass surfaces of the nanopipette is included together with the field effect through the glass wall to account for the electric double layer and the electro-osmosis. The inclusion of the field effect through the pipette wall is new compared to previous modeling of similar structures and is shown to be crucial for the behavior at the tip. It is demonstrated that the Concentration of molecules is a consequence of ionic charge accumulation at the tip screening the electric field, thereby slowing down the electrophoretic motion of the molecules, which is further slowed down or stopped by the oppositely directed electro-osmosis. It is also shown that the trapping is very sensitive to the properties of the molecule, that is, its electrophoretic mobility and diffusion coefficient, the properties of the pipette, the ionic strength of the solution, and the applied electric field.
