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Your search keyword '"Nielsen, Niels Chr."' showing total 475 results
Start Over Author "Nielsen, Niels Chr." Publication Type Academic Journals
475 results on '"Nielsen, Niels Chr."'

3. Light‐activated 3D printed fish‐like actuator.

Author

Pendlmayr, Stefan, Ramos‐Docampo, Miguel Alexandre, Bento, David H., Brodszkij, Edit, Juhl, Dennis Wilkens, Nielsen, Niels Chr, and Städler, Brigitte

Subjects
ACTUATORS, SOFT robotics, POLY(ISOPROPYLACRYLAMIDE), PHOTOTHERMAL effect, CRITICAL temperature, THREE-dimensional printing, BUFFER layers, ROBOTICS
Abstract

Hydrogel‐based actuators are innovative materials that exhibit responsive and dynamic behavior in response to external stimuli, making them promising candidates for a wide range of applications in fields such as soft robotics. We employ 3D printing to create layered rectangles, using a passive ink composed of gelatin methacryloyl (GelMA) and an active ink consisting of GelMA and poly(N‐isopropylacrylamide) (PNIPAM). Our aim is to assess and compare the bending capabilities of these structures based on their layer arrangements in a buffer above the lower critical solution temperature. Therefore, an asymmetric rectangular structure is selected as the shape‐changing component in the tail of a 3D printed fish‐shaped hydrogel actuator. We show that gold nanostars integrated into the actuators serve as photothermal elements, enabling the fish tail to repeatedly bend when near infrared light is turned on and off. Our effort illustrates the potential of combining 3D printing, responsive hydrogels and photothermal elements with near infrared light towards soft robotic applications. This combination yields actuators capable of shape‐shifting without requiring localized light or transitioning between environments with varying temperatures. [ABSTRACT FROM AUTHOR]

Published
2024
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25. A unified heteronuclear decoupling picture in solid-state NMR under low radio-frequency amplitude and fast magic-angle-spinning frequency regime.

Author

Sharma, Kshama, Equbal, Asif, Nielsen, Niels Chr., and Madhu, P. K.

Subjects
RADIO frequency, NUCLEAR spin, MAGIC angle spinning, COMPUTER simulation
Abstract

Heteronuclear spin decoupling is a highly important component of solid-state NMR experiments to remove undesired coupling interactions between unlike spins for spectral resolution. Recently, experiments using a unification strategy of standard decoupling schemes were presented for high radio-frequency (RF) amplitudes and slow-intermediate magic-angle-spinning (MAS) frequencies, in the pursuit of deeper understanding of spin decoupling under phase-modulated RF irradiation [A. Equbal et al., J. Chem. Phys. 142, 184201 (2015)]. The approach, unified two-pulse heteronuclear decoupling (UTPD), incorporates the simultaneous time- and phase-modulation strategies, commonly used in solid-state NMR. Here, the UTPD based decoupling scheme is extended to the experimentally increasingly important regime of low RF amplitudes and fast MAS frequencies. The unified decoupling approach becomes increasingly effective in identifying the deleterious dipole-dipole and, in particular, J recoupling conditions which become critical for the low-amplitude RF regime. This is because J coupling is isotropic and therefore not averaged out by sample spinning unlike the anisotropic dipole-dipole coupling. Numerical simulations and analytic theory are used to understand the effects of various nuclear spin interactions on the decoupling performance of UTPD, in particular, the crucial difference between the low-phase and high-phase UTPD conditions with respect to J coupling. In the UTPD scheme, when the cycle-frequency of the pulse-sequence is comparable to the RF nutation frequency, the existence of a non-zero effective rotation in the basic two-pulse scheme becomes an essential feature for the efficient and robust averaging out of the scalar J coupling. This broad viewpoint is expected to bring different optimum low-power decoupling pulse schemes under a common footing. [ABSTRACT FROM AUTHOR]

Published
2019
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47. Metabolomic signatures of inbreeding at benign and stressful temperatures in Drosophila melanogaster

Author

Pedersen, Kamilla Sofie, Kristensen, Torsten Nygaard, Loeschcke, Volker, Petersen, Bent O., Duus, Jens O., Nielsen, Niels Chr., and Malmendal, Anders

Subjects
Drosophila -- Genetic aspects, Metabolomics -- Research, Inbreeding -- Genetic aspects, Biological sciences
Abstract

While the population genetics of inbreeding is fairly well understood, the effects of inbreeding on the physiological and biochemical levels are not. Here we have investigated the effects of inbreeding on the Drosophila melanogaster metabolome. Metabolite fingerprints in males from five outbred and five inbred lines were studied by nuclear magnetic resonance spectroscopy after exposure to benign temperature, heat stress, or cold stress. In both the absence and the presence of temperature stress, metabolite levels were significantly different among inbred and outbred lines. The major effect of inbreeding was increased levels of maltose and decreased levels of 3-hydroxykynurenine and a galactoside [1-O-(4-O-(2-aminoethyl phosphate)-[beta]-D-galactopyranosyl)-x-glycerol] synthesized exclusively in the paragonial glands of Drosophila species, including D. melanogaster. The metabolomic effect of inbreeding at the benign temperature was related to gene expression data from the same inbred and outbred lines. Both gene expression and metabolite data indicate that fundamental metabolic processes are changed or modified by inbreeding. Apart from affecting mean metabolite levels, inbreeding led to an increased between-line variation in metabolite profiles compared to outbred lines. In contrast to previous observations revealing interactions between inbreeding and environmental stress on gene expression patterns and life-history traits, the effect of inbreeding on the metabolite profile was similar across the different temperature treatments.

Published
2008

48. Effect of magnetic field strength on NMR-based metabonomic human urine data. Comparative study of 250, 400, 500, and 800 MHz

Author

Bertram, Hanne Christine, Malmendal, Anders, Petersen, Bent O., Madsen, Jens Chr., Pedersen, Henrik, Nielsen, Niels Chr., Hoppe, Camilla, Molgaard, Christian, Michaelsen, Kim F., and Duus, Jens O.

Subjects
Nuclear magnetic resonance spectroscopy -- Research, Magnetic fields -- Influence, Metabonomic analysis -- Research, Urine -- Chemical properties, Spectra (Spectroscopy) -- Evaluation, Chemistry
Abstract

Metabonomic analysis of urine utilizing high-resolution NMR spectroscopy and chemometric techniques has proven valuable in characterizing the biochemical response to an intervention. To assess the effect of magnetic field strength on information contained in NMR-based metabonomic data sets, IH NMR spectra were acquired on 250-, 400-, 500-, and 800-MHz instruments, respectively, on the same set of human urine samples collected before and after dietary interventions with milk and with meat proteins. Partial least-squares regression discriminant analyses (PLS-DA) were performed in order to elucidate the ability of the [sup.1]H spectra acquired at various field strengths to identify possible spectral differences and discriminate between pre- and postintervention samples. The loadings from PLS-DA contained the same spectral regions, implying that the same metabolites were involved in the discrimination independent of magnetic field strength. The investigation revealed a strong increase in prediction performance and thereby spectral information content when increasing the magnetic field strength from 250 to 500 MHz, while from 500 to 800 MHz the increase was less pronounced.

Published
2007

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