The locations of Brønsted acid sites (BAS) in the channels of medium-pore zeolites have a significant effect on the spontaneous ionization of para-terphenyl (PP(3)) insofar as spatial constraints determine the stability of transition states and charge-transfer complexes relevant to charge separation. The ionization rates and ionization yield values demonstrate that a strong synergy exists between the H(+) polarization energy and spatial constraints imposed by the channel topology. Spectroscopic and modeling results show that PP(3) incorporation, charge separation, charge transfer and charge recombination differ dramatically among zeolites with respect to channel structure (H-FER, H-MFI, H-MOR) and BAS density in the channel. Compartmentalization of ejected electrons away from the initial site of ionization decreases dramatically the propensity for charge recombination. The main mode of PP(3)(.+) decay is hole transfer to form AlO(4)H(.+) ⋅⋅⋅PP(3) charge-transfer complexes characterized by intense absorption in the visible range. According to the nonadiabatic electron-transfer theory, the small reorganization energy in constrained channels explains the slow hole-transfer rate.
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Sci Rep
January 2025
College of Architecture and Urban Planning, Guizhou University, Guiyang, 550025, China.
Karst small towns globally face challenges due to limited disaster-resilient resources, making it difficult to handle increasingly severe disaster environments. Improving the efficiency of disaster-resilient resource utilization and maintaining a tight balance state of disaster-resilient resources (TBS) are crucial for enhancing disaster adaptability and resilience. This study used urban and disaster data from a representative karst region in China (2017-2021) to conduct a quantitative analysis of TBS in karst small towns, exploring the mechanisms and interactions within this state and identifying obstacle factors.
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January 2025
Westchase Software, Houston, TX, 77063, USA.
It is well known that the sedimentary rock record is both incomplete and biased by spatially highly variable rates of sedimentation. Without absolute age constraints of sufficient resolution, the temporal correlation of spatially disjunct records is therefore problematic and uncertain, but these effects have rarely been analysed quantitatively using signal processing methods. Here we use a computational process model to illustrate and analyse how spatial and temporal geochemical records can be biased by the inherent, heterogenous processes of marine sedimentation and preservation.
View Article and Find Full Text PDFNeural Netw
December 2024
Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. Electronic address:
Manual annotation of ultrasound images relies on expert knowledge and requires significant time and financial resources. Semi-supervised learning (SSL) exploits large amounts of unlabeled data to improve model performance under limited labeled data. However, it faces two challenges: fusion of contextual information at multiple scales and bias of spatial information between multiple objects.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
Institute of Science and Technology Austria, Klosterneuburg AT-3400, Austria.
Many biological systems operate near the physical limits to their performance, suggesting that aspects of their behavior and underlying mechanisms could be derived from optimization principles. However, such principles have often been applied only in simplified models. Here, we explore a detailed mechanistic model of the gap gene network in the embryo, optimizing its 50+ parameters to maximize the information that gene expression levels provide about nuclear positions.
View Article and Find Full Text PDFAlzheimers Dement
December 2024
Institute of Brain Sciene, National Yang Ming Chiao Tung University, Taipei, Taiwan.
Background: Genome-wide association studies demonstrated that immune suppressive receptor CD33 variants are associated with high susceptibility to developing Alzheimer's disease (AD). Human CD33 (hCD33) regulates microglial immune response and clearance ability. However, the differential regulation of phagocytosis by human and mouse CD33 imposes constraints on utilizing the mouse model for investigating the role of CD33 in AD.
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