10 results on '"Zhang, Shuyu"'
Search Results
2. Localized State-Induced Enhanced Emission in Perovskite Nanocrystals
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Wang, Feilong, Ou, Qiongrong, and Zhang, Shuyu
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The luminescent mechanism of nano-sized materials with indirect bandgap and parity-forbidden transition has always been a critical issue in breaking through bottlenecks in traditional luminescent materials. The lack of understanding has resulted in great disputes regarding the origin of fluorescence in weak-transition nanocrystals (NCs). This paper proposes a new physical luminescence model, named as localized state-induced enhanced emission (LIEE), i.e., localized processes induced by size-limitation or partial doping, to explain the anomalous luminescence from non-luminescent state to luminescent state in various perovskite nanocrystals with indirect/direct bandgap or parity-forbidden transition. These findings provide a theoretical viewpoint to design efficient lead-free perovskite NCs and promote the development of fast optical transitions in luminescent materials.
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- 2024
3. Proton-CAT: a Novel Strategy for Enhanced Proton Therapy
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Sun, Zhao, He, Zhencen, He, Zhuohang, Wu, Junxiang, Deng, Liyuan, Chen, Ziqi, Jiang, Junkang, Zhu, Hang, Zhang, Shuyu, and Hu, Zhimin
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Physics - Medical Physics ,Physics - Applied Physics - Abstract
We present a nitrogen-targeting-Proton-Carbon-Alpha-Therapy method, abbreviated as Proton-CAT, which partially converts protons into carbon-12 and $\alpha$ particles through nuclear reactions between protons and nitrogen-15. Monte Carlo simulations validated the effectiveness of the Proton-CAT, and the study specifically focused on the distribution of relative energy deposition. The results indicated that the presence of nitrogen-15 enhanced the maximum dose level of protons, resulting in more effective damage confined to tumor cells. Statistical analysis of secondary ions has shown that the Proton-CAT significantly increases the production efficiencies of carbon-12 and $\alpha$ particles. Furthermore, it has been revealed that elevating the nitrogen-15 concentration significantly boosts the dose of carbon and $\alpha$ particles within the tumor region. The present work would contribute to the future development of proton therapy., Comment: 5 pages, 4figures
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- 2024
4. Effect of the ${\rm^{15}N(p,\alpha)^{12}C}$ reaction on the kinetic energy release of water molecule fragmentation
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He, Zhuohang, He, Zhencen, Duan, Mingliang, Wu, Junxiang, Deng, Liyuan, Chen, Ziqi, Zhang, Shuyu, and Hu, Zhimin
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Physics - Chemical Physics ,Physics - Atomic and Molecular Clusters - Abstract
In this work, we investigated the effect of ${\rm^{15}N(p,\alpha)^{12}C}$ reaction produced by the collision between proton and ammonia monohydrate on the kinetic energy release (KER) of water molecule fragmentation. After the occurrence of the nuclear reaction, it was found that the charge states $q$ and the flight speeds $v$ are the main factors affecting the KER of water molecule fragmentation. With the value of $q/v$ increases, the KER distribution gets wider and the peak position changes more pronounced. The energy gained by each fragment is related to the mass of the fragment and the distance of the fragment from the nuclear reaction. In this study, the fragments with smaller masses and the distances far away from the nuclear reaction get higher energies. The fragments of water molecules getting higher energy may induce other factors affecting the radiotherapy effect, which needs more detailed investigations in the future.
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- 2024
5. Spontaneous symmetry breaking on surface defects
- Author
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Cuomo, Gabriel and Zhang, Shuyu
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High Energy Physics - Theory ,Condensed Matter - Statistical Mechanics ,Condensed Matter - Strongly Correlated Electrons - Abstract
Coleman's theorem states that continuous internal symmetries cannot be spontaneously broken in two-dimensional quantum field theories (QFTs). In this work we consider surface (i.e. two-dimensional) defects in $d$-dimensional conformal field theories (CFTs) invariant under a continuous internal symmetry group $G$. We study under which conditions it is possible for a surface defect to break spontaneously a continuous internal symmetry. We find that spontaneous symmetry breaking (SSB) is impossible under reasonable assumptions on the defect Renormalization Group (RG) flow. Counterexamples are possible only for exotic RG flows, that do not terminate at a fixed-point. We discuss an example of this kind. We also illustrate our no-go result with an effective field theory analysis of generic defect RG flows. We find a generic weakly coupled defect universality class (with no SSB), where correlation functions decay logarithmically. Our analysis generalizes the recent discovery by Metlitski of the extraordinary-log boundary universality class in the $O(N)$ model., Comment: 37 pages+appendices, 3 figures, v2 several minor edits, v3 added app. B and minor edits, journal version
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- 2023
6. Localized State-Induced Enhanced Intrinsic Phonon-Free Optical Transition in Silicon Nanocrystals
- Author
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Wang, Feilong, Ou, Qiongrong, and Zhang, Shuyu
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Silicon photoluminescence and lasing have been critical issues to breakthrough bottlenecks in the understanding of luminescence mechanisms. Unfortunately, long-standing disputes about the exciton recombination mechanism and fluorescence lifetime remain unresolved, especially about whether silicon nanocrystals (Si NCs) can realize fast direct-bandgap-like optical transitions. Here, using ground-state and excited-state density functional theory (DFT), we obtained intrinsic phonon-free optical transitions at sizes from Si22 to Si705, showing that very small Si NCs can realize a strong direct optical transition. Orbital labeling results show that this rapid transition does not come from the {\Gamma}-{\Gamma} -like transition, contrary to the conclusions from the effective mass approximation (EMA) and that {\Gamma}-X mixing leads to a quasi-direct bandgap. This anomalous transition is particularly intense with decreasing size (or enhancement of quantum confinement). By investigating electron and hole distributions generated in the optical transition, localized state-induced enhanced emission (LIEE) in Si NCs was proposed. Quantum confinement (QC) distorts the excited-state electron spatial distribution by localizing Bloch waves into the NC core, resulting in increased hole and electron overlap, thus inducing a fast optical process. This work resolves important debates and proposes LIEE to explain the anomalous luminescence--a phase transition from weak (or none) luminescent state to strong optical transition, which will aid attempts at realizing high-radiative-rate NCs materials and application-level Si lasers.
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- 2022
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7. Privacy-preserving Traffic Flow Prediction: A Federated Learning Approach
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Liu, Yi, Yu, James J. Q., Kang, Jiawen, Niyato, Dusit, and Zhang, Shuyu
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Computer Science - Machine Learning ,Computer Science - Cryptography and Security ,Statistics - Machine Learning - Abstract
Existing traffic flow forecasting approaches by deep learning models achieve excellent success based on a large volume of datasets gathered by governments and organizations. However, these datasets may contain lots of user's private data, which is challenging the current prediction approaches as user privacy is calling for the public concern in recent years. Therefore, how to develop accurate traffic prediction while preserving privacy is a significant problem to be solved, and there is a trade-off between these two objectives. To address this challenge, we introduce a privacy-preserving machine learning technique named federated learning and propose a Federated Learning-based Gated Recurrent Unit neural network algorithm (FedGRU) for traffic flow prediction. FedGRU differs from current centralized learning methods and updates universal learning models through a secure parameter aggregation mechanism rather than directly sharing raw data among organizations. In the secure parameter aggregation mechanism, we adopt a Federated Averaging algorithm to reduce the communication overhead during the model parameter transmission process. Furthermore, we design a Joint Announcement Protocol to improve the scalability of FedGRU. We also propose an ensemble clustering-based scheme for traffic flow prediction by grouping the organizations into clusters before applying FedGRU algorithm. Through extensive case studies on a real-world dataset, it is shown that FedGRU's prediction accuracy is 90.96% higher than the advanced deep learning models, which confirm that FedGRU can achieve accurate and timely traffic prediction without compromising the privacy and security of raw data., Comment: This paper is in the second round of under review of the IEEE Internet of Things Journal
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- 2020
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8. Compositional representation of protein sequences and the number of Eulerian loops
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Hao, Bailin, Xie, Huimin, and Zhang, Shuyu
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Physics - Biological Physics ,Quantitative Biology - Abstract
An amino acid sequence of a protein may be decomposed into consecutive overlapping strings of length K. How unique is the converse, i.e., reconstruction of amino acid sequences using the set of K-strings obtained in the decomposition? This problem may be transformed into the problem of counting the number of Eulerian loops in an Euler graph, though the well-known formula must be modified. By exhaustive enumeration and by using the modified formula we show that the reconstruction is unique at K equal or greater than 5 for an overwhelming majority of the proteins in the PDB.seq database. The corresponding Euler graphs provide a means to study the structure of repeated segments in protein sequences., Comment: 5 pages, no figure, 2 tables, RevTex3.1
- Published
- 2001
9. Characteristics of Placebo Responders in Pediatric Clinical Trials of Attention-Deficit/Hyperactivity Disorder
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Newcorn, Jeffrey H., Sutton, Virginia K., and Zhang, Shuyu
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Objective: Understanding placebo response is a prerequisite to improving clinical trial methodology. Data from placebo-controlled trials of atomoxetine in the treatment of children and adolescents with attention-deficit/hyperactivity disorder (ADHD) were analyzed to identify demographic and clinical characteristics that might predict placebo response in future clinical trials. Method: Data were pooled across 731 placebo-treated pediatric patients who participated in 10 acute, randomized, placebo-controlled trials. Responder status was based on empirically derived thresholds of change on the total score of the ADHD Rating Scale with minimal and robust response defined as 25% or greater and 40% or greater decrease, respectively. Study design characteristics, including randomization ratio, dose, and titration strategy, and patient demographic and clinical characteristics were examined as potential predictors of placebo response. Results: Inattentive subtype, lack of previous stimulant treatment, presence of comorbid tics and nonwhite ethnicity were associated with robust placebo response. A subset analysis of patients completing 6 weeks of treatment (to eliminate the effects of early dropout) identified inattentive subtype and lack of previous stimulant experience as significant predictors of robust placebo response. Conclusions: Placebo response is less likely in subjects with combined-subtype ADHD who are not stimulant-naive. Limiting ADHD clinical trials to this more restricted subject group is likely to maximize treatment differences. However, because this is not always possible or desirable, identifying other methods of mitigating placebo response is essential. (Contains 2 tables.)
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- 2009
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10. Comparison of Symptomatic versus Functional Changes in Children and Adolescents with ADHD during Randomized, Double-Blind Treatment with Psychostimulants, Atomoxetine, or Placebo
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Buitelaar, Jan K., Wilens, Timothy E., and Zhang, Shuyu
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Background: This meta-analysis was designed to determine the relationship between reduction of attention-deficit/hyperactivity disorder (ADHD) symptoms and improvement in functioning by examining short-term changes in functional and symptomatic scores in children and adolescents with ADHD. Methods: Search of atomoxetine's clinical trial database identified four studies involving a symptomatic measure, the ADHD Rating Scale-IV-Parent Version:Investigator-administered and -scored (ADHDRS-IV-Parent:Inv), and a functional measure, the Life Participation Scale for ADHD (LPS). Results: Correlation analysis revealed a moderate-to-strong association between changes in the LPS total versus ADHDRS-IV-Parent:Inv total (r: -0.68). The LPS "Self-control" subscale showed higher correlations than the "Happy/Social" subscale with the symptomatic measures. Regression analysis also showed high sensitivity for functional measures to changes in symptom severity. Stratified analysis of mean changes in ADHDRS-IV-Parent:Inv scores corresponding to standardized changes in LPS functional scores indicated that a threshold reduction of 16-18 points on the ADHDRS-IV-Parent:Inv total score was needed for functional improvements to become evident. Conclusions: Subjects' symptomatic improvements appear to be reflected in improvements in their social and behavioral function as measured by the LPS. These initial findings warrant verification by replication with other outcome measures.
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- 2009
- Full Text
- View/download PDF
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