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"Model Law"
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Investigation of Effective Thermal Conductivity for Ordered and Randomly Packed Bed with Thermal Resistance Network Method
In the present paper, the effective thermal conductivities of Li4SiO4-packed beds with both ordered and random packing structures were investigated using thermal resistance network methods based on both an Ohm’s law model and a Kirchhoff’s law model. The calculation results were also validated and compared with the numerical and experimental results. Firstly, it is proved that the thermal resistance network method based on the Kirchhoff’s law model proposed in the present study is reliable and accurate for prediction of effective thermal conductivities in a Li4SiO4-packed bed, while the results calculated with the Ohm’s law model underestimate both ordered and random packings. Therefore, when establishing a thermal resistance network, the thermal resistances should be connected along the main heat transfer direction and other heat transfer directions as well in the packing unit. Otherwise, both the total heat flux and effective thermal conductivity in the packing unit will be underestimated. Secondly, it is found that the effect of the packing factor is remarkable. The effective thermal conductivity of a packed bed would increase as the packing factor increases. Compared with random packing at similar packing factor, the effective thermal conductivity of packed bed would be further improved with an ordered packing method.
Journal Article
Using river discharge to model and deconstruct the latitudinal diversity gradient for fishes of the Western Hemisphere
AIM: To model the species–discharge relationship (SDR) for native freshwater fishes of the Western Hemisphere, to test whether the SDR is itself a function of latitude, and to create a conceptual framework to integrate the SDR with the species–area relationship and the latitudinal diversity gradient. LOCATION: Western Hemisphere rivers between 70°N and 50°S latitude. METHODS: Discharge and fish richness data were compiled for 107 rivers. Ordinary least squares and simultaneous autoregressive models were built for a hemispheric‐scale SDR using one of three discharge (Q) measures: mean annual Q, annual low flow Q or annual high flow Q. Hemispheric‐scale SDR residuals were used to test for distinct low, mid and high latitude groups and to deconstruct the SDR into separate models for each latitudinal group. Structural equation modelling (SEM) was then used to examine the combined effects of Q, river basin area, and latitude on fish richness. RESULTS: Hemispheric‐scale SDRs were significant (P ≤ 0.001) for each discharge measure. Model residuals showed that the SDR differs among tropical, subtropical and temperate realms. All deconstructed SDRs remained significant (P ≤ 0.001) and minimized the residual effect of latitude. The tropical SDR was significantly steeper (non‐overlapping 95% confidence intervals) than the subtropical and temperate SDRs. For both hemispheric‐scale and deconstructed SDRs, annual low flow Q was the best individual predictor of native fish richness. SEM analysis showed that Q may be an integrative measure of climate and physical habitat effects. MAIN CONCLUSIONS: A single, hemispheric‐scale SDR will underestimate fish richness in low latitude, tropical rivers and overestimate richness in high latitude, temperate rivers. Deconstructing the SDR into separate tropical, subtropical, and temperate models can account for much of this bias. Deconstructed SDRs also show that fish richness increases much more rapidly per‐unit Q in tropical rivers than in subtropical or temperate rivers. Low flow Q is the strongest correlate of fish richness. And a preliminary, system‐level model suggests that Q may play a central, integrative role in the regulation of freshwater diversity.
Journal Article
Self-organization of genic and intergenic sequence lengths in genomes: Statistical properties and linguistic coherence
In a genome, genes (coding constituents) are interrupted by intergenic regions (noncoding constituents). This study provides a general picture of the large‐scale self‐organization of coding, noncoding, and total constituent lengths in genomes. Ten model genomes were examined and strong correlations between the number of genomic constituents and the constituent lengths were observed. The analysis was carried out by adopting a linguistic distribution model and a structural analogy between linguistic and genomic constructs. The proposed linguistic‐based statistical analysis may provide a fundamental basis for both understanding the linear structural formation of genomic constituents and developing insightful strategies to figure out the function of genic and intergenic regions in genomic sequences. © 2014 Wiley Periodicals, Inc. Complexity 21: 268–282, 2015
Journal Article
Utilization of Bracing Arms as Additional Reinforcement in Pultruded Glass Fiber-Reinforced Polymer Composite Cross-Arms: Creep Experimental and Numerical Analyses
The application of pultruded glass fiber-reinforced polymer composites (PGFRPCs) as a replacement for conventional wooden cross-arms in transmission towers is relatively new. Although numerous studies have conducted creep tests on coupon-scale PGFRPC cross-arms, none had performed creep analyses on full-scale PGFRPC cross-arms under actual working load conditions. Thus, this work proposed to study the influence of an additional bracing system on the creep responses of PGFRPC cross-arms in a 132 kV transmission tower. The creep behaviors and responses of the main members in current and braced PGFRPC cross-arm designs were compared and evaluated in a transmission tower under actual working conditions. These PGFRPC cross-arms were subjected to actual working loads mimicking the actual weight of electrical cables and insulators for a duration of 1000 h. The cross-arms were installed on a custom test rig in an open area to simulate the actual environment of tropical climate conditions. Further creep analysis was performed by using Findley and Burger models on the basis of experimental data to link instantaneous and extended (transient and viscoelastic) creep strains. The addition of braced arms to the structure reduced the total strain of a cross-arm’s main member beams and improved elastic and viscous moduli. The addition of bracing arms improved the structural integrity and stiffness of the cross-arm structure. The findings of this study suggested that the use of a bracing system in cross-arm structures could prolong the structures’ service life and subsequently reduce maintenance effort and cost for long-term applications in transmission towers.
Journal Article
Sustained fitness gains and variability in fitness trajectories in the long-term evolution experiment with Escherichia coli
Many populations live in environments subject to frequent biotic and abiotic changes. Nonetheless, it is interesting to ask whether an evolving population's mean fitness can increase indefinitely, and potentially without any limit, even in a constant environment. A recent study showed that fitness trajectories of Escherichia coli populations over 50 000 generations were better described by a power-law model than by a hyperbolic model. According to the power-law model, the rate of fitness gain declines over time but fitness has no upper limit, whereas the hyperbolic model implies a hard limit. Here, we examine whether the previously estimated power-law model predicts the fitness trajectory for an additional 10 000 generations. To that end, we conducted more than 1100 new competitive fitness assays. Consistent with the previous study, the power-law model fits the new data better than the hyperbolic model. We also analysed the variability in fitness among populations, finding subtle, but significant, heterogeneity in mean fitness. Some, but not all, of this variation reflects differences in mutation rate that evolved over time. Taken together, our results imply that both adaptation and divergence can continue indefinitely—or at least for a long time—even in a constant environment.
Journal Article
Establishment of the African Medicines Agency: progress, challenges and regulatory readiness
Insufficient access to quality, safe, efficacious and affordable medical products in Africa has posed a significant challenge to public health for decades. In part, this is attributed to weak or absent policies and regulatory systems, a lack of competent regulatory professionals in National Medicines Regulatory Authorities (NMRAs) and ineffective regional collaborations among NMRAs. In response to national regulatory challenges in Africa, a number of regional harmonisation efforts were introduced through the African Medicines Regulatory Harmonisation (AMRH) initiative to, among others, expedite market authorisation of medical products and to facilitate the alignment of national legislative frameworks with the AU Model Law on Medical Products Regulation. The goals of the model law include to increase collaboration across countries and to facilitate the overall regional harmonisation process. The AMRH initiative is proposed to serve as the foundation for the establishment of the African Medicines Agency (AMA). The AMA will, as one of its mandates, coordinate the regional harmonisation systems that are enabled by AU Model Law domestication and implementation. In this paper, we review the key entities involved in regional and continental harmonisation of medicines regulation, the milestones achieved in establishing the AMA as well as the implementation targets and anticipated challenges related to the AU Model Law domestication and the AMA’s establishment. This review shows that implementation targets for the AU Model Law have not been fully met, and the AMA treaty has not been ratified by the minimum required number of countries for its establishment. In spite of the challenges, the AU Model Law and the AMA hold promise to address gaps and inconsistencies in national regulatory legislation as well as to ensure effective medicines regulation by galvanising technical support, regulatory expertise and resources at a continental level. Furthermore, this review provides recommendations for future research.
Journal Article
Gravitational waves in f(R) gravity power law model
We investigate the different polarization modes of gravitational waves in f(R) gravity power law model in de Sitter space. It is seen that the massive scalar field polarization mode exists in this model. The mass of the scalar field depends highly on the background curvature and the power term n. However, we found that the model does not exhibit a massive scalar mode for n=2 and instead, it shows a breathing mode in addition to the tensor plus and cross modes. Thus, mass of the scalar field is found to vary with n within the range 1≤n≤2 .
Journal Article