4,237 research outputs found
Paradigm change in hydrogel sensor manufacturing: from recipe-driven to specification-driven process optimization
The volume production of industrial hydrogel sensors lacks a quality-assuring
manufacturing technique for thin polymer films with reproducible properties.
Overcoming this problem requires a paradigm change from the current
recipe-driven manufacturing process to a specification-driven one. This
requires techniques to measure quality-determining hydrogel film properties
as well as tools and methods for the control and optimization of the
manufacturing process. In this paper we present an approach that
comprehensively addresses these issues. The influence of process parameters
on the hydrogel film properties and the resulting sensor characteristics have
been assessed by means of batch manufacturing tests and the application of
several measurement techniques. Based on these investigations, we present
novel methods and a tool for the optimization of the
cross-linking process step, with the latter being crucial for the sensor
sensitivity. Our approach is applicable to various sensor designs with
different hydrogels. It has been successfully tested with a sensor solution
for surface technology based on PVA/PAA hydrogel as sensing layer and a
piezoelectric thickness shear resonator as transducer. Finally, unresolved
issues regarding the measurement of hydrogel film parameters are outlined for
future research
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Paradigm change in hydrogel sensor manufacturing: From recipe-driven to specification-driven process optimization
The volume production of industrial hydrogel sensors lacks a quality-assuring manufacturing technique for thin polymer films with reproducible properties. Overcoming this problem requires a paradigm change from the current recipe-driven manufacturing process to a specification-driven one. This requires techniques to measure quality-determining hydrogel film properties as well as tools and methods for the control and optimization of the manufacturing process. In this paper we present an approach that comprehensively addresses these issues. The influence of process parameters on the hydrogel film properties and the resulting sensor characteristics have been assessed by means of batch manufacturing tests and the application of several measurement techniques. Based on these investigations, we present novel methods and a tool for the optimization of the cross-linking process step, with the latter being crucial for the sensor sensitivity. Our approach is applicable to various sensor designs with different hydrogels. It has been successfully tested with a sensor solution for surface technology based on PVA/PAA hydrogel as sensing layer and a piezoelectric thickness shear resonator as transducer. Finally, unresolved issues regarding the measurement of hydrogel film parameters are outlined for future research
Asymptotically free scalar curvature-ghost coupling in Quantum Einstein Gravity
We consider the asymptotic-safety scenario for quantum gravity which
constructs a non-perturbatively renormalisable quantum gravity theory with the
help of the functional renormalisation group. We verify the existence of a
non-Gaussian fixed point and include a running curvature-ghost coupling as a
first step towards the flow of the ghost sector of the theory. We find that the
scalar curvature-ghost coupling is asymptotically free and RG relevant in the
ultraviolet. Most importantly, the property of asymptotic safety discovered so
far within the Einstein-Hilbert truncation and beyond remains stable under the
inclusion of the ghost flow.Comment: 8 pages, 3 figures, RevTe
Structural and Magnetic Dynamics in the Magnetic Shape Memory Alloy NiMnGa
Magnetic shape memory Heusler alloys are multiferroics stabilized by the
correlations between electronic, magnetic and structural order. To study these
correlations we use time resolved x-ray diffraction and magneto-optical Kerr
effect experiments to measure the laser induced dynamics in a Heusler alloy
NiMnGa film and reveal a set of timescales intrinsic to the system. We
observe a coherent phonon which we identify as the amplitudon of the modulated
structure and an ultrafast phase transition leading to a quenching of the
incommensurate modulation within 300~fs with a recovery time of a few ps. The
thermally driven martensitic transition to the high temperature cubic phase
proceeds via nucleation within a few ps and domain growth limited by the speed
of sound. The demagnetization time is 320~fs, which is comparable to the
quenching of the structural modulation.Comment: 5 pages, 3 figures. Supplementary materials 5 pages, 5 figure
Does Digoxin Provide Additional Hemodynamic and Autonomic Benefit at Higher Doses in Patients With Mild to Moderate Heart Failure and Normal Sinus Rhythm?
AbstractObjectives. This study sought to examine the hemodynamic and autonomic dose response to digoxin.Background. Previous studies have demonstrated an increase in contractility and heart rate variability with digitalis preparations. However, little is known about the dose-response to digoxin, which has a narrow therapeutic window.Methods. Nineteen patients with moderate heart failure and a left ventricular ejection fraction <0.45 were studied hemodynamically using echocardiography and blood pressure at baseline and after 2 weeks of low dose (0.125 mg daily) and 2 weeks of moderate dose digoxin (0.25 mg daily). Loading conditions were altered with nitroprusside at each study. Autonomic function was studied by assessing heart rate variability on 24-h Holter monitoring and plasma norepinephrine levels during supine rest.Results. Low dose digoxin provided a significant increase in ventricular performance, but no further increase was seen with the moderate dose. Low dose digoxin reduced heart rate and increased heart rate variability. Moderate dose digoxin produced no additional increase in heart rate variability or reduction in sympathetic activity, as manifested by heart rate, plasma norepinephrine or low frequency/high frequency power ratio. In addition, we did not find that either low or moderate dose digoxin increased parasympathetic activity.Conclusions. We conclude that moderate dose digoxin provides no additional hemodynamic or autonomic benefit for patients with mild to moderate heart failure over low dose digoxin. Because higher doses of digoxin may predispose to arrhythmogenesis, lower dose digoxin should be considered in patients with mild to moderate heart failure.(J Am Coll Cardiol 1997;29:1206–13
Unraveling the structural complexity in a single-stranded RNA tail: implications for efficient ligand binding in the prequeuosine riboswitch
Single-stranded RNAs (ssRNAs) are ubiquitous RNA elements that serve diverse functional roles. Much of our understanding of ssRNA conformational behavior is limited to structures in which ssRNA directly engages in tertiary interactions or is recognized by proteins. Little is known about the structural and dynamic behavior of free ssRNAs at atomic resolution. Here, we report the collaborative application of nuclear magnetic resonance (NMR) and replica exchange molecular dynamics (REMD) simulations to characterize the 12 nt ssRNA tail derived from the prequeuosine riboswitch. NMR carbon spin relaxation data and residual dipolar coupling measurements reveal a flexible yet stacked core adopting an A-form-like conformation, with the level of order decreasing toward the terminal ends. An A-to-C mutation within the polyadenine tract alters the observed dynamics consistent with the introduction of a dynamic kink. Pre-ordering of the tail may increase the efficacy of ligand binding above that achieved by a random-coil ssRNA. The REMD simulations recapitulate important trends in the NMR data, but suggest more internal motions than inferred from the NMR analysis. Our study unmasks a previously unappreciated level of complexity in ssRNA, which we believe will also serve as an excellent model system for testing and developing computational force fields
Raman and Computational Study on the Adsorption of Xanthine on Silver Nanocolloids
Xanthine is a nucleobase, deriving from adenine and guanine by deamination and oxidation processes, which may deposit in the human body causing diseases, similar to uric acid. Here, we have investigated the adsorption of xanthine on silver colloidal nanoparticles by means of surface-enhanced Raman scattering (SERS) with an exciting radiation in the near-infrared spectral region, where interference due to fluorescence does not occur, along with density functional theory calculations of molecule/metal model systems. By adopting a combined experimental and computational approach, we have identified the "marker" SERS bands of xanthine and the tautomer that preferentially binds the silver particles, as well as the molecular group involved in the interaction with metal. This investigation allows using the FT-SERS spectroscopy for biosensory and diagnostic purposes in body fluids, detecting abnormal levels of xanthine, and preventing metabolic diseases
The Fourth VLBA Calibrator Survey - VCS4
This paper presents the fourth extension to the Very Long Baseline Array
(VLBA) Calibrator Survey, containing 258 new sources not previously observed
with very long baseline interferometry (VLBI). This survey, based on three 24
hour VLBA observing sessions, fills remaining areas on the sky above
declination -40 degrees where the calibrator density is less than one source
within a 4 degree radius disk at any given direction. The share of these area
was reduced from 4.6% to 1.9%. Source positions were derived from astrometric
analysis of group delays determined at 2.3 and 8.6 GHz frequency bands using
the Calc/Solve software package. The VCS4 catalogue of source positions, plots
of correlated flux density versus projected baseline length, contour plots and
fits files of naturally weighted CLEAN images, as well as calibrated visibility
function files are available on the Web at http://gemini.gsfc.nasa.gov/vcs4 .Comment: 8 pages, 8 figures, 3 tables, accepted for publication in the
Astronomical Journal; minor changes to the text are made, table 2 in
electronic form is added and can be extracted from the preprint sourc
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