| 51841. |
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| 51842. |
- Ludwig, Jean, et al.
(författare)
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The C*-algebras of the Heisenberg group and of thread-like Lie groups
- 2011
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Ingår i: Mathematische Zeitschrift. - : Springer Science and Business Media LLC. - 0025-5874 .- 1432-1823. ; 268, s. 897-930
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Tidskriftsartikel (refereegranskat)abstract
- We describe the C∗-algebras of the Heisenberg group Hn, n ≥ 1, and the threadlike Lie groups GN , N ≥ 3, in terms of C∗-algebras of operator fields.
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| 51843. |
- Ludwig, Markus, et al.
(författare)
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Ultraviolet astronomical spectrograph calibration with laser frequency combs from nanophotonic lithium niobate waveguides
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Astronomical precision spectroscopy underpins searches for life beyond Earth, direct observation of the expanding Universe and constraining the potential variability of physical constants on cosmological scales. Laser frequency combs can provide the required accurate and precise calibration to the astronomical spectrographs. For cosmological studies, extending the calibration with such astrocombs to the ultraviolet spectral range is desirable, however, strong material dispersion and large spectral separation from the established infrared laser oscillators have made this challenging. Here, we demonstrate astronomical spectrograph calibration with an astrocomb in the ultraviolet spectral range below 400 nm. This is accomplished via chip-integrated highly nonlinear photonics in periodically-poled, nano-fabricated lithium niobate waveguides in conjunction with a robust infrared electro-optic comb generator, as well as a chip-integrated microresonator comb. These results demonstrate a viable route towards astronomical precision spectroscopy in the ultraviolet and could contribute to unlock the full potential of next-generation ground-based and future space-based instruments.
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| 51844. |
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| 51845. |
- Luengo, Alba, et al.
(författare)
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Increased demand for NAD + relative to ATP drives aerobic glycolysis
- 2021
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-4164 .- 1097-2765. ; 81:4, s. 691-707.e6
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Tidskriftsartikel (refereegranskat)abstract
- Aerobic glycolysis, or preferential fermentation of glucose-derived pyruvate to lactate despite available oxygen, is associated with proliferation across many organisms and conditions. To better understand that association, we examined the metabolic consequence of activating the pyruvate dehydrogenase complex (PDH) to increase pyruvate oxidation at the expense of fermentation. We find that increasing PDH activity impairs cell proliferation by reducing the NAD+/NADH ratio. This change in NAD+/NADH is caused by increased mitochondrial membrane potential that impairs mitochondrial electron transport and NAD+ regeneration. Uncoupling respiration from ATP synthesis or increasing ATP hydrolysis restores NAD+/NADH homeostasis and proliferation even when glucose oxidation is increased. These data suggest that when demand for NAD+ to support oxidation reactions exceeds the rate of ATP turnover in cells, NAD+ regeneration by mitochondrial respiration becomes constrained, promoting fermentation, despite available oxygen. This argues that cells engage in aerobic glycolysis when the demand for NAD+ is in excess of the demand for ATP. Aerobic glycolysis is associated with proliferation in many biological contexts, yet what drives this phenotype has not been fully explained. Luengo et al. show that cells engage in aerobic glycolysis when the demand for NAD+ exceeds the demand for ATP, which leads to impaired NAD+ regeneration by mitochondrial respiration.
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| 51846. |
- Luft, Matthias, et al.
(författare)
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Proof of concept for multiple nerve transfers to a single target muscle
- 2021
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Ingår i: eLife. - 2050-084X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Surgical nerve transfers are used to efficiently treat peripheral nerve injuries, neuromas, phantom limb pain, or improve bionic prosthetic control. Commonly, one donor nerve is transferred to one target muscle. However, the transfer of multiple nerves onto a single target muscle may increase the number of muscle signals for myoelectric prosthetic control and facilitate the treatment of multiple neuromas. Currently, no experimental models are available. This study describes a novel experimental model to investigate the neurophysiological effects of peripheral double nerve transfers to a common target muscle. In 62 male Sprague-Dawley rats, the ulnar nerve of the antebrachium alone (n=30) or together with the anterior interosseus nerve (n=32) was transferred to reinnervate the long head of the biceps brachii. Before neurotization, the motor branch to the biceps' long head was transected at the motor entry point. Twelve weeks after surgery, muscle response to neurotomy, behavioral testing, retrograde labeling, and structural analyses were performed to assess reinnervation. These analyses indicated that all nerves successfully reinnervated the target muscle. No aberrant reinnervation was observed by the originally innervating nerve. Our observations suggest a minimal burden for the animal with no signs of functional deficit in daily activities or auto-mutilation in both procedures. Furthermore, standard neurophysiological analyses for nerve and muscle regeneration were applicable. This newly developed nerve transfer model allows for the reliable and standardized investigation of neural and functional changes following the transfer of multiple donor nerves to one target muscle.
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| 51847. |
- Lugez, C.L., et al.
(författare)
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Infrared spectra of (NO)(2)(+), (NO)(2)(-), and (NO)(3)(-) trapped in solid neon
- 1999
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Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 110:21, s. 10345-10358
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Tidskriftsartikel (refereegranskat)abstract
- New studies of the infrared spectra of the products which result on codeposition at approximately 5 K of a Ne:NO sample with Ne atoms that have been excited in a microwave discharge have led to new and revised assignments for several ionic species. The appearance of the ν1 absorption of ONNO+ for several new species with asymmetric isotopic substitution, but for no symmetrically substituted species, confirms the trans ground-state configuration for ONNO+. The behavior of a neon-matrix product absorption at 1227.5 cm−1 parallels that of an argon-matrix absorption at 1221.0 cm−1 which has recently been assigned to trans-ONNO−. The identity of the carrier of a product absorption at 1424.1 cm−1, contributed by a vibration of two symmetrically equivalent NO groups, has not been definitively established. This absorption exhibits complex photodestruction behavior. Three absorptions are assigned to cis,cis-(NO)3−, which has C2v symmetry, with the aid of density functional calculations of the isotopic substitution pattern for the vibrational fundamentals of this species. Similar calculations of the isotopic substitution patterns for other structures result in poor agreement with the experiments. Photodestruction of cis,cis-(NO)3− trapped in solid neon yields the N2O⋯NO2− complex.
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| 51848. |
- Lui, H., et al.
(författare)
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Antenna configurations of microwave breast imaging
- 2013
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Ingår i: 2013 3rd Asia-Pacific Microwave Conference, APMC 2013; Seoul; South Korea; 5 November 2013 through 8 November 2013. - 9781479914746 ; , s. 1188-1190
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Konferensbidrag (refereegranskat)abstract
- The quality of the forward scattering data is crucial for the microwave breast imaging. Early study showed that the quality of the forward data varies in different polarization basis. In the actual imaging scenarios where antenna arrays are usually required, mutual coupling effects between the antenna elements would affect the quality of the forward data and thus the resultant images. Here, we aim to determine how the array size and thus the mutual coupling could impact on the forward data. The forward problems of different array configurations are studied and evaluated via full-wave numerical simulations, and found that small arrays with stronger coupling are preferred. © 2013 IEEE.
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| 51849. |
- Lui, H., et al.
(författare)
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Mutual Coupling in Antenna Arrays 2013
- 2014
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2014
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The invention of antenna arrays opened up the door for microwave sensing and communications. Most applications of antenna arrays are in the defense and wireless communications areas. The introduction of multiple-input-multiple-output (MIMO) concept in recent years has opened up further opportunities in that the system performance can be maintained with a smaller number of antennas. The existence of mutual coupling effect, that is, the electromagnetic interaction between antenna elements, appears as an undesirable effect in most of these cases. The transmitted and received signals can be significantly distorted such that the signals no longer depend solely on the antenna elements, but also on the array structure and the surrounding environment. Such distortions result in the reduction of channel capacities in communications applications, as well as poor accuracies in ranging and direction finding. In most applications, the mutual coupling effect is unknown. A major challenge is then to characterize this undesirable effect and to accurately estimate the unknown parameters (range, direction) without a priori knowledge of the signal environment.This special issue, which is the third one in its series, provides an international forum for researchers to disseminate their results and ideas to tackle some of these challenging research problems. Five dedicated papers have contributed to this special issue. These papers concern the mutual coupling and its impacts on MIMO communications, direction finding, and MIMO radar. To help interested readers with a quick reference to the main themes of these papers, we briefly introduce them as follows.The first paper entitled “Self-interference cancellation-based mutual-coupling model for full-duplex single-channel MIMO systems,” concerns the mutual coupling problem in MIMO communications. The paper addresses the self-interference and mutual-interference of a full-duplex single-channel MIMO communications system.In the presence of mutual coupling, the array manifold is perturbed, which results in poor accuracies in direction finding. The paper “Accurate DOA estimations using microstrip adaptive arrays in the presence of mutual coupling effect” proposes a method to calibrate the undesirable mutual coupling effect for arrays with non-omni-directional radiating elements. The third paper, entitled “2-D direction of arrival estimation for cross array in the presence of mutual coupling,” introduces a noniterative algorithm based on the Propagation Method for accurate two-dimensional direction finding problems using a cross array in the presence of mutual coupling. The paper “AR model-based direction-of-arrival estimation of coherent signals in the presence of unknown mutual coupling” provides a novel signal processing solution based on a spatial autoregression (AR) model for coherent direction finding of uniform linear arrays.The fifth paper of this special issue, entitled “Root-MUSIC based angle estimation for MIMO radar with unknown mutual coupling,” explores the direction finding solutions in MIMO radar. A Root-MUSIC based solution is proposed to estimate the incoming signal direction with unknown mutual coupling.All papers appearing in this special issue have been subject to a strict peer-reviewing process. They are of high quality and address the mutual coupling problem from different perspectives. Through this special issue, we have provided a medium of dissemination for valuable ideas and conclusions on mutual coupling research. At the same time, we hope that more research innovations can be stimulated for future advances on this subject.
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| 51850. |
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