Zhong Chen

Bio: Zhong Chen is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Medicine & Chemistry. The author has an hindex of 80, co-authored 1000 publications receiving 28171 citations. Previous affiliations of Zhong Chen include Institute of High Performance Computing Singapore & National Institute of Education.

Numerical simulations of contribution of chemical shift in novel magnetic resonance imaging

Abstract: Contribution of chemical shift to intermolecular multiple-quantum coherence (iMQC) imaging signals in two-component systems was simulated and discussed using an efficient numerical algorithm based on the Bloch equations with an additional nonlinear term describing distant dipolar field. Numerical simulation switches back and forth between real and Fourier spaces to handle dipolar field effects in three-dimensional sample. The iMQC signals of each component of two-component systems can be obtained respectively when the second pulse of the CRAZED pulse sequence is selective. Simulation results show that chemical shift provides an edge detection method to regions containing spins with chemical shift offset and selected by the second RF pulse, and different gray value is related to different chemical shift in detected regions. These results indicate that chemical shift may provide new imaging information helpful for iMQC magnetic resonance imaging.

Management of acute exacerbation of chronic obstructive pulmonary disease under a tiered medical system in China

Abstract: Background: The Chinese government has promoted the ‘tiered medical services’ policy in which diseases are classified by severity, mode of onset and difficulty of treatment since 2015 to optimize medical resources. We evaluated the diagnosis and treatment of acute exacerbation (AE) of chronic obstructive pulmonary disease (AECOPD) under the tiered system. Methods: We conducted a cross-sectional study. COPD characteristics and treatments were compared among hospitals in different tiers. Associations were examined by univariate and multivariable logistic regression analysis. In addition, multivariate logistic regression was performed to identify the possible influencing factors of antibiotics, glucocorticoids and anticoagulant usages. Results: Eligible COPD patients (n = 432) were consecutively recruited from eight hospitals in different tiers in China. Patients in the countryside preferred the community hospitals, whereas patients in cities preferred second-tier and teaching hospitals when they suffer from AECOPD. It indicates most COPD patients are likely to treat their disease locally. The severity of COPD AE increased with tiers of hospitals (p < 0.001). However, our results clearly show that most community hospitals can only deal with mild exacerbation of COPD. Approximately 90% of AE patients received antibiotics. We speculated that antibiotics abuse might exist in the three tiers of hospitals. Multivariate analysis demonstrated that long-term antibiotics usage (⩾14 days) was associated with moderate exacerbation [odds ratio (OR): 5.295, 95% confidence intervals (CI) 2.248–12.473, p < 0.001], radiographic progression (OR: 2.176, 95% CI: 1.047–4.522, p = 0.037), positive sputum etiology (OR: 3.073, 95% CI: 1.477–6.394, p = 0.003) and increased white blood cells (OR: 2.470, 95% CI: 1.190–5.126, p = 0.015). The proportion of glucocorticoids increased with the hospital hierarchy (18.6% versus 45.6% versus 69.2%, p < 0.001). The proportions of severe cases in the second-tier hospitals were 26.9%; however, non-invasive positive pressure ventilation (NPPV) rate was only 14.7%. Anticoagulant is not commonly used in AECOPD, and the community hospitals had the lowest proportion of anticoagulation regimen (1.7% versus 14.3% versus 20.5%, p = 0.002). Conclusions: The ‘tiered medical services’ policy in AECOPD management has been unsatisfactory in the past years. Irrational treatment strategies in different hospitals were still found when comparing with international guideline. Further reform of the policy is still needed to optimize the management of AECOPD in China.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...