In this discourse, we would like to discuss some issues of concept and principle in the context of the following three aspects. One, how [Formula: see text] arises as a constant of space-time structure on the same footing as the velocity of light. These are the two constants innate to space-time without reference to any force or dynamics whatsoever, and are interwoven in the geometry of 'free' homogeneous space-time. Two, how does the vacuum energy gravitate? Could its gravitational interaction in principle be included in general relativity or a new theory of quantum space-time/gravity would be required? Finally, we would like to raise the fundamental question: How does the Universe physically expand? Since there does not lie anything outside into which it can expand, instead it has to expand on its own-maybe by creating new space-time out of nothing at each instant and at every location! Thus not only was the Universe created at some instant in the past marking the beginning in the Big Bang, it is in fact being created continuously at each epoch as it expands. We thus need quantum theory of space-time/gravity for fully understanding the working of the Universe. This article is part of the theme issue 'The future of mathematical cosmology, Volume 2'.
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http://dx.doi.org/10.1098/rsta.2021.0405 | DOI Listing |
Adv Sci (Weinh)
January 2025
Shaanxi Key Laboratory of Artificially Structured Functional Materials and Devices, Airforce Engineering University, Xi'an, Shaanxi, 710051, China.
The integrated modulation of radiation and scattering provides an unprecedented opportunity to reduce the number of electromagnetic (EM) apertures in the platform while simultaneously enhancing communication and stealth performance. Nevertheless, achieving full-polarization, arbitrary amplitude, and phase modulation of radiation scattering remains a challenge. In this paper, a strategy that realizes space-time coding of radiation scattering within the same frequency band, which enables the simultaneous and independent modulation of amplitude and phase, is proposed.
View Article and Find Full Text PDFJ Biotechnol
January 2025
Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China; The Research Center of Chiral Drugs, Shanghai Frontiers Science Center for TCM Chemical Biology, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China. Electronic address:
Chiral azacyclic amine derivatives occupy a vital role of nitrogen-containing compounds, due to serve as foundational motifs in numerous pharmaceuticals and bioactive substances. Novel complementary enantioselective reductive aminases IRED9 and IRED11 were unveiled through comprehensive gene mining from Streptomyces viridochromogenes and Micromonospora echinaurantiaca, respectively, which both demonstrated enantiomeric excess (ee) values and conversion ratios of up to 99 % towards N-Boc-3-pyridinone (NBPO) and cyclopropylamine. IRED9 exhibited the highest activity at pH 8.
View Article and Find Full Text PDFSci Adv
January 2025
School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA.
Using time as an additional design parameter in electromagnetism, photonics, and wave physics is attracting considerable research interest, motivated by the possibility to explore physical phenomena and engineering opportunities beyond the limits of time-invariant systems. Here, we report the experimental demonstration of enhanced broadband absorption of electromagnetic waves in a continuously modulated time-varying system, exceeding one of the key theoretical limits of linear time-invariant absorbers. This is achieved by harnessing the frequency-wave vector transitions and enhanced interference effects enabled by breaking both continuous space- and time-translation symmetries in a periodically time-modulated absorbing structure operating at radio frequencies.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), State Key Laboratory of Chemical Engineering, Haihe Laboratory of Sustainable Chemical Transformations, Tianjin Key Laboratory of Applied Catalysis Science and Engineering, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P. R. China.
CO hydrogenation to methanol using green hydrogen derived from renewable resources provides a promising method for sustainable carbon cycle but suffers from high selectivity towards byproduct CO. Here, we develop an efficient PdZn-ZnO/TiO catalyst by engineering lattice dislocation structures of TiO support. We discover that this modification orders irregularly arranged atoms in TiO to stabilize crystal lattice, and consequently weakens electronic interactions with supported active phases.
View Article and Find Full Text PDFBioorg Chem
February 2025
School of Biotechnology and Key Laboratory of Industrial Biotechnology of Education, School of Biotechnology, Jiangnan University, Wuxi 214122 China. Electronic address:
Achieving enzyme catalysis at high substrate concentrations is a substantial challenge in industrial biocatalysis, and the role of glycosylation in post-translational modifications that modulate enzyme substrate inhibition remains poorly understood. This study provides insights into the role of N-glycosylation in substrate inhibition by comparing the catalytic properties of d-lactonohydrolase (d-Lac) derived from Fusarium moniliforme expressed in prokaryotic and eukaryotic hosts. Experimental evidence indicates that recombinant d-Lac expressed in Pichia pastoris (PpLac-WT) exhibits higher hydrolysis rates at a substrate concentration of 400 g/L, with reduced substrate inhibition and enhanced stability compared to the recombinant d-Lac expressed in Escherichia coli (EcLac-WT).
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