445 research outputs found
Coupled mesoscale analysis of concrete shrinkage
No full textCracking, driven by shrinkage and thermal strains, strongly influences the serviceability and durability of concrete structures. After several decades of use, cracking can cause structural deterioration and damage. Concrete shrinkage is sensitive to temperature and humidity variations in a complex hygrothermal environment. Therefore, an efficient numerical framework is essential to predict the structural response for all potential geometries and environmental conditions. This work presents a new multi-physics simulation framework coupling the mechanical behavior with chemical/physical processes of concrete while considering the meso-structure of concrete. The Lattice Discrete Particle Model (LDPM) is used the describe the mechanical response. The Hygro-Thermo-Chemical (HTC) model, which describes the moisture transport, heat transfer, and curing reaction, is solved using a flow lattice element (FLE) system dual to the mechanical mesh. The development of mechanical characteristics, as well as thermal and hygral eigenstrains owing to continued curing, is driven by the HTC model. In addition, a newly proposed 2-phase formulation for concrete shrinkage is introduced, considering the effect of aggregate volume and stiffness on concrete shrinkage. The results give robust predictions of macroscopic shrinkage for concretes with different mix proportions and indicate a better representation of meso-structural features than the previously proposed 1-phase formulation. To ensure the reliability of the results, five experimental campaigns from the literature were selected to calibrate and validate the numerical model. The model agrees well with the experimental data and offers new insights into local strain distribution and cracking behavior in heterogeneous materials at an acceptable computational cost
Post-transcriptional gene silencing in plants: a double-edged sword
No full textIn plants, post-transcriptional gene silencing (PTGS) protects the genome from foreign genes and restricts the expression of certain endogenous genes for proper development. Here, we review the recent progress about how the unwanted PTGS is avoided in plants. As a decision-making step of PTGS, aberrant transcripts from most endogenous coding genes are strictly sorted to the bidirectional RNA decay pathways in cytoplasm but not to the short interference RNA (siRNA)-mediated PTGS, with the exception of a few development-relevant endogenous siRNA-producing genes. We also discuss a finely balanced PTGS threshold model that plants fully take advantage of the power of PTGS without self-harm.National Basic Research Program of China [2012CB910902]; National Natural Science Foundation of China [91217305, 91017010]SCI(E)PubMed中国科学引文数据库(CSCD)[email protected]
Application-oriented microfluidic LOC devices for the detection of microorganisms, toxic chemicals and serological biomarkers
No full textLab-on-a-chip (LOC) technology has advanced over the past several decades. As miniaturized multiphase multistep reactors, LOCs are suitable for the implementation of complex liquid phase reactions in the field of biomedical detection. This doctoral thesis focused on the development of new LOC devices and relevant functionalities for various application cases, including microbe detection, water-safety testing, while also presenting preliminary studies on the measurement of signal molecules in blood.
The application-oriented R&D (research and development) strategy was employed in the studies on a series of biomedical LOC devices. Technological challenges, e.g. optimization of on-chip quantification NASBA (nucleic acid sequence-based amplification) protocols, system design etc. were resolved in individual cases. Based on a low-cost R&D strategy, most LOCs in this doctoral work were developed for bench-top equipment as disposable components. It is worth noting that a methodological concept is also developed and summarized in this thesis, i.e., the selection of decision support mechanisms (DSMs) for biomedical LOC devices.
The DSM is the supporting mechanism generating measurable signals in the LOC, and translating them into a meaningful conclusion, which can help users to make decisions in the real application field. Namely, DSMs can enable LOC-based testing and are thus a distinguished feature of application-oriented LOC devices. The author categorized the research achievements presented in this thesis into three distinctive classes, as follows:
1) Conventional DSMs commonly employed in current biomedical experimental approaches.
Articles I, II and III focus on this category of DSMs. The series of LOCs in these reports were modelled on standard microtiter plates, and thus these chips are completely compatible with the microplate readers commonly utilized in biological laboratories. Article I reported the design, fabrication and validation of a disposable 43-chamber LOC device for quantitative detection of waterborne pathogens. Its principle was similar to conventional ELISA(enzyme-linked immunosorbent assay) tests for microbes, entitled X. Zhao: Application-oriented microfluidic LOC devices for the detection of microorganisms, toxic chemicals and serological biomarkers immuno-NASBA assay. A synthetic peptide and two common waterborne pathogens (Escherichia coli and rotavirus) in artificial samples were used to validate the LOC functions, which indicated that the LOC device has the potential to quantify traces of waterborne pathogens with high specificity.
Article II described the development of a LOC platform for environmental investigations into aquatic microorganisms, on the basis of quantitative NASBA (Q-NASBA). The LOC system was composed of a membrane-based sampling module, a sample preparation cassette, and a 24-channel Q-NASBA chip. The DSM of the LOC was derived from the polyurethane-foam-unit (PFU) method, which has been widely used to evaluate environmental pollution in fresh water. The multifunctional system could simplify and standardize the complicated processes of microbial detection.
Article III addressed the implementation of a 384-chamber microfluidic simulator with the incorporated functions of pathogen identification and antimicrobial susceptibility testing (AST) for personalizing the antibiotic treatment of urinary tract infections (UTIs). Its DSM adopted the diagnosis principle of conventional ATP bioluminescence assay (ATP-BLA) for living microbial cells.
2) Unconventional DSMs for contrived LOC systems. The second class of biomedical LOCs employs tailored DSMs, which are still derived from known working principles. However, the concrete mechanisms and diagnostic criteria are arbitrary in contrived functional LOCs.
Article IV investigated a bioluminescent-cell-based continuous-flow device, termed a ‘living-cell chip’, with a self defining DSM to implement real-time broad-spectrum online monitoring of water quality. The prototype integrated a T-junction droplet generator, counter-flow micro-mixers, and time-delay channels. The LOC device can mix the water sample and Vibrio fischeri cell sensors into a droplet flow, and incubate the droplets in the time-delay channels before optical detection. Its DSM relies upon the relationship between the toxicant concentration in the water sample and the relative luminescence units of the bioluminescent cells in the running droplets, which is obviously different from the conventional intermittent method of ISO11384. The proposed LOC system shows great promise for an early warning system against potential toxicant chemicals in drinking water.
3) Developing prognostic/diagnosis DSMs for biomedical-database-dependent LOC systems with the aid of computational modelling. The third category relies on computational modelling within a large-scale medical/healthcare database, which is currently emerging and is not yet completely developed.
Article V reported a pilot study on the design and fabrication of the LOC device for signal molecule profiling in blood.
Articles VI proposed the potential roadmap and preliminary experimental approach for the construction of a human signal-molecule-profiling database (HSMPD) by the use of the former LOC device, leading to prognostic/diagnosis DSMs in the future
Analysis of Ionomic Profiles of Spinal Cords in a Rat Model with Bone Cancer Pain
No full textJinlu Huang,1,* Jiugeng Chen,2,* Le Ma,3,* Xieyi Zhu,4 Lili Wan,1 Xinyan Li,4 Cheng Guo1 1Department of Pharmacy, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, People’s Republic of China; 2Instrumental Analysis Center, Shanghai Jiao Tong University, Shanghai, People’s Republic of China; 3Department of Pharmacy, Shanghai Jiao Tong University School of Medicine, Shanghai Mental Health Center, Shanghai, People’s Republic of China; 4College of Pharmacy, Shanghai Jiao Tong University, Shanghai, People’s Republic of China*These authors contributed equally to this workCorrespondence: Xinyan Li; Cheng Guo, Email [email protected]; [email protected]: Ionomics is used to study levels of ionome in different states of organisms and their correlations. Bone cancer pain (BCP) severely reduces quality of life of patients or their lifespan. However, the relationship between BCP and ionome remains unclear.Methods: The BCP rat model was constructed through inoculation of Walker 256 cells into the left tibia. Von Frey test, whole-cell patch-clamp recording and inductively coupled plasma mass spectrometry (ICP-MS) technologies were conducted for measuring tactile hypersensitivity, the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) of neurons of spinal slices, and ionome of spinal cord samples, respectively. Principal component analysis (PCA) was used to explore ionomic patterns of the spinal cord.Results: The BCP rat model was successfully constructed through implantation of Walker 256 cells into the left tibia. The frequency and amplitude of mEPSCs of neurons in the spinal cord slices from the BCP model rats were notably greater than those in the sham control. In terms of ionomics, the spinal cord levels of two macroelements (Ca and S), four microelements (Fe, Mn, Li and Sr) and the toxic element Ti in the BCP group of rats were significantly increased by inoculation of Walker 256 cancer cells, compared to the sham control. In addition, the correlation patterns between the elements were greatly changed between the sham control and BCP groups. PCA showed that inoculation of Walker 256 cells into the tibia altered the overall ionomic profiles of the spinal cord. There was a significant separation trend between the two groups.Conclusion: Taken together, inoculation of Walker 256 cells into the left tibia contributes to BCP, which could be closely correlated by some elements. The findings provided novel information on the relationship between the ionome and BCP.Keywords: bone cancer pain, spinal cord, micronutrient, ionomic profil
Construction and Validation of the Integration Model of Planned Behavior Theory and Health Belief Model
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Research on Perceived Profiles and Stages of Exercise Behavior Change in Urban Residents
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From Segregation to Integration: Planning and Designing for the Enhancement of Socio-spatial and Ecological Integration in Haizhu District, China
No full textThe discontinuities of urban development and city expansion reveal Haizhu a fragmented and diverse area that results in disparity and isolation in different communities and social groups, and decreasing green and blue spaces. The objective of this thesis is to create an integrated and comprehensive socio-ecological network in terms of corridor and node at multiple scales that can improve the socio-spatial integration and reconnect the fragmented green and blue spaces for Haizhu district. Corridor is creating a linear connection or movement between spaces with certain buffer area to surrounding context instead of just a linear feature as boundary, while node provides certain places where nature or people can integrate with each other.Architecture, Urbanism and Building Sciences | Transitional Territorie
The Source and the nature of life and consciousness
No full textIt seems to the author that, though it is possible to reach an explanation of consciousness, there is no direct way for us to go. In other words, the author believes that, only through a detour, through an understanding of everything outside mind, we may and can and will finally reach an understanding of those inside.
The author tries in this article to discuss some details of such a detour, first from the understanding of Being and being, universe and life, organism and human, and finally to the understanding of the mind and the mystery of our consciousness.
Here, to understand Being is the core activities of the whole detour, and there the being is understandably the source and the nature of life and consciousness
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