Recent Advances in Bioactive Artificial Ionophores

Several life-threatening diseases, also known as ‘Channelopathies’ are linked to irregularities in ion transport proteins. Significant research efforts have fostered the development of artificial transport systems that facilitates to restore the functions of impaired natural transport proteins. Indeed, a few of these artificial ionophores demonstrate the rare combination of transmembrane ion transport and important biological activity, offering early promises of suitability in ‘channel replacement therapy’. In this review, structural facets and functions of both cationophores and anionophores are discussed. Ionophores that are toxic to various bacteria and yeast, could be exploited as antimicrobial agent. Nevertheless, few non-toxic ionophores offer the likelihood of treating a wide range of genetic diseases caused by the gene mutations. In addition, their ability to disrupt cellular homeostasis and to alter lysosomal pH endow ionophores as promising candidates for cancer treatment. Overall, critically outlining the advances in artificial ionophores in terms of in vitro ion transport, possible modes of action and biological activities enables us to propose possible future roadmaps in this research area.     

Energy savings in a building using regenerative evaporative cooling

This paper explores the potential of reducing the annual energy consumption of a central air-conditioned building through advanced evaporative cooling systems. The building considered is a typical three floor library building of a University. The regenerative evaporative cooling technology is coupled with the liquid cooled water chiller system to accomplish the energy conservation objective. Comparisons of the regenerative evaporative cooling are made with simple evaporative cooling to bring out the importance such a system. The well-known building simulation software, TRNSYS is used to carry out the heat load calculations and the dynamic simulations of the building. Annual energy consumptions of different components of the air-conditioning system are estimated for the existing water chiller system as well as for both coupled evaporative cooling systems (simple and regenerative). The annual energy consumptions, the indoor temperature, the relative humidity and the thermal comfort index ‘PMV’ are compared for all the three different air-conditioning systems. The coupling of direct and regenerative evaporative cooling technologies with water chiller system has shown, respectively, 12.09% and 15.69% savings in annual energy consumption of the building, while maintaining PMV between ?1 and +1 for most of the hours in the year.     

Numerical and experimental data set for benchmarking hygroscopic buffering models

This paper presents experimental data measured in a bed of gypsum boards in the transient moisture transfer (TMT) facility at the University of Saskatchewan. The relative humidity and temperature were measured at two depths in a gypsum bed and the moisture accumulation was measured for the entire bed. Experiments were conducted for both coated (acrylic and latex paint) and uncoated gypsum. These experimental data are compared to simulated data from eight different numerical models. The agreement between the experimental and numerical data is good and often within the experimental uncertainty bounds. A sensitivity analysis was performed to show the influence of material properties such as sorption, vapour permeability and the transfer coefficients on the simulated results. One model examines hysteresis of the sorption isotherm.     

A Non‐Mulberry Silk Fibroin Protein Based 3D In Vitro Tumor Model for Evaluation of Anticancer Drug Activity

The limitations of clinical chemotherapy are credited primarily to drug resistance. Effective development and screening of new drugs require appropriate in vitro tumor models that resemble the in vivo situation to evaluate drug efficiency and to decrease the use of experimental animals. 3D in vitro model systems that are able to mimic in vivo microenvironments are now highly sought after in cancer research. Here, the characteristics of breast cancer cell line MDA‐MB‐231 cells on 3D, and 2D Antheraea mylitta silk matrices and tissue culture plates are compared. After long term culture of breast cancer cells in the silk scaffold, the engineered tumor construct shows different zones of cell proliferation, such as an avascular tumor. Silk fibroin matrix 3D tumor models are studied for the evaluation of various anticancer drugs. The cytotoxic effects of three different drugs (Paclitaxel, Celecoxib, and ZD6474) at different concentrations are evaluated for MDA‐MB‐231 grown on 2D films as well as on a 3D fibroin scaffold. Higher drug concentrations are required to achieve a comparable reduction in cell viability and invasive potential in 3D culture. Combinatorial treatment of drugs at IC₅₀ concentrations result in up to 84% death of cancer cells. The results indicate that 3D in vitro tumor models may be better systems to evaluate cancer treatment strategies.     

Analytic representation of dynamical systems using pseudo-inverse methods

Summary The term `analytic representation' in configuration space is often used for the representation of a physical system in terms of Lagrangians and/or Lagrange's equations. Such representations play a role in the methodological formulation for a wide variety of physical problems. We deal with two different approaches to construct Lagrangians for a number of equations. Examples cited cover both point and continuum mechanics. This work will be of special significance to those who would like to study problems of contemporary physics without being directly involved in the rigorous theory of Helmholtz for inverse variational problems. The first procedure chosen by us depends on the method of characteristics as used for solving first order partial differential equations while the second one exploits the symmetries of the Lagrangian and the equation of motion. For simple cases, both approaches are applicable without any modification. However, in more realistic situations the methods need to be supplemented by some ansatz.     

An experimental data set for benchmarking 1-D, transient heat and moisture transfer models of hygroscopic building materials. Part II: Experimental, numerical and analytical data

This paper presents the experimental results on spruce plywood and cellulose insulation using the transient moisture transfer (TMT) facility presented in Part I [P. Talukdar, S.O. Olutmayin, O.F. Osanyintola, C.J. Simonson, An experimental data set for benchmarking 1-D, transient heat and moisture transfer models of hygroscopic building materials-Part-I: experimental facility and property data, Int. J. Heat Mass Transfer, in press, doi:10.1016/j.ijheatmasstransfer.2007.03.026] of this paper. The temperature, relative humidity and moisture accumulation distributions within both materials are presented following different and repeated step changes in air humidity and different airflow Reynolds numbers above the materials. The experimental data are compared with numerical data, numerical sensitivity studies and analytical solutions to increase the confidence in the experimental data set.     

单壁碳纳米管的力学性能、断裂和屈服行为与其几何形貌的关系

采用分子动力学模拟研究了单壁碳纳米管的力学特性与其长度、直径及手性的关系.在施加拉伸或压缩载荷时,不同直径的单壁碳纳米管表现出明确的力学性能变化.锯齿型和扶手椅型碳纳米管的拉伸性能与其长度无关,而对于手性碳纳米管来说则稍有变化.所有类型碳纳米管的压缩特性,主要是刚度和临界压应力均随碳纳米管长度的变化而改变.断裂模式因结构不同而异,屈服过程产生纽结、波浪状结构、柱状屈曲、弯曲和扭曲等.     

Combined radiation and convection heat transfer in a porous channel bounded by isothermal parallel plates

Combined radiation and convection heat transfer in a porous medium confined between gray isothermal parallel plates is investigated. The medium is absorbing, emitting and scattering. Cases of boundaries at temperatures higher or lower than the medium are considered. In the porous medium, the boundary effect on the fully developed laminar velocity field as proposed by Kaviany is accounted for. For various values of the extinction coefficient, the scattering albedo, the conduction-radiation parameter and the boundary emissivity, Nusselt number, temperature and heat flux distributions are found for the range of values including the extreme limits of the porous medium shape parameter (PMSP), γ=(W²φ/K)^1/2, where W is the channel width, φ the porosity and K the permeability. For the lower limiting value of the PMSP γ, the effect of the porous medium is negligible and the situation approaches that of Poiseuille flow. For this limiting case, results from the present work are compared with those available in the literature. For medium to high values of the PMSP γ, for the purpose of comparison, some results are presented in tabular form. Radiation is found to have a significant effect on various parameters studied. The discrete transfer method was used for the solution of the radiative part of the energy equation. An iterative finite difference scheme was used to solve the energy equation.