Model hysteresis dimer molecule I: Equilibrium properties

A Hamiltonian system describing hysteresis behavior in a dimeric chemical reaction is modeled in a MD simulation utilizing novel two-body potentials with switches that is particularly suitable for numerical thermodynamical investigations. It is surmized that such reaction mechanisms could exist in nature on the basis of recent experiments, which indicate that electromagnetic hysteresis behavior is exhibited at the molecular level, although experimental interpretations tend to construct models that avoid such mechanisms. Numerical results of various common equilibrium thermodynamical and kinetic properties are presented together with new algorithms that were implemented to compute these quantities, where no unusual thermodynamics was observed for the chemical reaction which might be interpreted as not being “time reversible invariant” and therefore susceptible to manifesting unusual thermodynamical phenomena, which might contradict any of the known laws of thermodynamics. A revision of the concept of “time reversibility” to accommodate the above results is suggested. The general design of the reaction mechanism also allows for the use of conventional potentials and by the utilization of switches, overcomes the bottleneck of computations which involves multi-body interactions. The initial theoretical, program and algorithm development was done at Norwegian University of Science and Technology-NTNU, Institute of Physical Chemistry, (Trondheim, Norway) during a sabbatical visit 2000–2001 financed by University of Malaya. The method of MD used here conforms to the periodic boundary conditions and thermostatting algorithms developed or refined by Ikeshoji and Hafskjold for standard, non-reacting particles. Their approach is non-synthetic using traditional Verlet integration of Newton’s equations of motion.     

Molecular assessment of S1 endonuclease-resistant snapback hairpin loops generated by DNA polymerase I during the in-vitro nick translation reaction

The in-vitro nick translation reaction used to label DNA to high specific activity also produces aberrant DNA structures known as “snapback” hairpin loops. Hairpin structures are precluded from participating in precise DNA-DNA hybridization interactions. Three nick translation systems were all found to yield significant quantities of snapback hairpins, as determined by their resistance to S1 endonuclease digestion following denaturation. The relative quantities of hairpins produced correlated with both the mass average size of the final DNA probe product synthesized as well as the overall rate of the nick translation reaction. Decreases in the amount of exogenous DNase I used in nick translation reactions produced significant decreases in the amount of hairpin loop structures formed. Hairpins could be effectively removed from nick-translated DNAs by employing hydroxylapatite column chromatography. Strategies to reduce hairpin formation during nick translation and the removal of hairpins from nick-translated DNAs are presented.     

The Pore Structure Determination of Carbon Aerogels

The detailed adsorption isotherms of nitrogen on carbon aerogels at 77 K were measured. The N2 adsorption isotherm had a marked hysteresis. The adsorption isotherms were analyzed by high resolution s-plots to evaluate their porosity. The s-plots showed an explicit upward deviation from the linearity below s = 0.5, suggesting the presence of micropores. The mesoporosity and microporosity were separately determined from the s-plot. The predominant pores in carbon aerogels were mesopores and the percentage of micropores was in the range of 5 to 10% of the total pore volume. The N2 adsorption hysteresis was analyzed with the Saam-Cole theory under the assumption of the cylindrical pore shape. The parameters determined from the Saam-Cole method were associated with the carbon aerogel structure.     

新型"分子合金"类Fe(II)配合物的合成和自旋转换性能

合成了Fe[(Htrz)~9~/~4(NH~2trz)~3~/~4](BF~4)~2.H~2O(1)和Fe[(Htrz)~3~/~2(NH~2trz)](BF~4).3H~2O(2)两个"分子合金"类自旋转换配合物。其变温光谱表明,它们在室温附近具有自旋转换行为,同时还伴有热致变色及滞后现象。     

Electrodynamics of interacting point charges: Excellence of the 1865 clausius approximation

Clausius force as equivalent to a time-instant Lorentz force. Action-reaction opposition expressed with the help of potential momenta QA. Conservation of a system's total mass, linear, angular and barycentric momenta. Automatic rendering of the 1967 hidden momentum in magnets effect. Clausius formalism asthe low velocity approximation to the Wheeler-Feynman electrodyanmics.     

Cleavage of RNA bulge loops by artificial RNases

Sensitivity of phosphodiester bonds in RNA bulge loops to cleavage by short cationic peptides and compounds based on 1,4-diazabicyclo[2.2.2]octane and its conjugates with imidazole was studied. Bulge loops containing from one to seven nucleotides were formed in RNA upon its hybridization with partially complementary oligodeoxyribonucleotides. The efficiency of RNA cleavage depends on the length of a bulge loop, the position of the cleaved phosphodiester bond in the loop, and the nature of the RNA-binding fragment of chemical ribonuclease (1,4-diazabicyclo[2.2.2]octane or a cationic peptide). In the absence of Mg²⁺ ions, the phosphodiester bond in the CA motif located in the apical position in 4-, 6-, or 7-membered loops is cleaved with the highest efficiency. In the presence of magnesium ions, the selectivity of RNA cleavage within bulge loops is substantially enhanced. In the case of 1,4-diazabicyclo[2.2.2]octane-based compounds, RNA is subjected to cleavage predominantly at the bonds in 4-, 6-, and 7-membered loops, whereas cleavage of other bonds is greatly suppressed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1236–1246, July, 2006.     

Developments and structures of mesopores in alkaline-treated ZSM-5 zeolites

ZSM-5 zeolites with SiO₂/Al₂O₃ molar ratio of 24 were treated in 0.05 M aqueous sodium hydroxide solution at 325 K in different periods. The samples were characterized by means of nitrogen adsorption at 77 K, field emission scanning electron microscopy, X-ray diffractometry, and Fourier transform infrared spectroscopy. Analysis of the experimental results showed that the alkaline treatment periods have influence on the developments and structures of mesopores in the alkaline-treated ZSM-5 zeolites. Alkaline treatment initially develops mesopores mainly from the boundary portion of MFI zeolites to the bulk, while prolonged treatment destroys the mesopores, and an optimum mesoporosity is obtained by the treatment for 1.5 h. On the other hand, crystallinities and short-range order in alkaline treated zeolites have remained virtually unchanged according to the examination from X-ray diffractometry and Fourier transform infrared spectroscopy.     

超疏水表面的研究进展

表面的浸润性是决定材料应用的一个重要性质,许多物理化学过程,如吸附、润滑、黏合、分散和摩擦等均与表面的浸润性密切相关.近年来,由于超疏水表面在自清洁表面、微流体系统和生物相容性等方面的潜在应用,有关超疏水表面的研究引起了极大的关注.本文综述了超疏水表面研究的新进展:简单介绍了表面浸润性的表征手段和影响因素,归纳了超疏水表面的制备方法和相关的理论分析,对超疏水表面研究的发展进行了展望.     

Microtextured superhydrophobic surfaces: a thermodynamic analysis

Superhydrophobic surfaces with a contact angle (CA) larger than 150 degrees have recently attracted great interest in both academic research and practical applications due to their water-repellent or self-cleaning properties. However, thermodynamic mechanisms responsible for the effects of various factors such as surface geometry and chemistry, liquids, and environmental sources have not been well understood. In this study, a pillar microtexture, which has been intensively investigated in experiments, is chosen as a typical example and thermodynamically analyzed in detail. To gain a comprehensive insight into superhydrophobic behavior, the roles of pillar height, width and spacing (or roughness and solid fraction), intrinsic CA, drop size, and vibrational energy are systematically investigated. Free energy (FE) and free energy barrier (FEB) are calculated using a simple and robust model. Based on the calculations of FE and FEB, various CAs, including apparent, equilibrium (stable), advancing and receding CAs, and contact angle hysteresis (CAH) can be determined. Especially, the design of practical superhydrophobic surfaces is emphasized in connection with the transition between noncomposite and composite states; a criterion for judging such transition is proposed. The theoretical results are consistent with the Wenzel's and the Cassie's equations for equilibrium CA values and experimental observations. Furthermore, based on these results and the proposed criterion, some general principles to achieve superhydrophobic performance are suggested.     

Droplet manipulation with bioinspired liquid-infused surfaces: A review of recent progress and potential for integrated detection

Point-of-need (PON) diagnostics offer promising methods to gather information relevant to health and safety on-site without the requirement for a fully equipped laboratory. In this review, we discuss how liquid-infused surfaces offer a promising platform to expand the capabilities of PON devices in the areas of biological sample preparation and system integration, providing new methods of controlling the movement of droplets and facilitating detection of biological and chemical compounds contained therein. Modifications to the underlying surface structure can be used to passively control the direction of droplet movement, and the careful selection of responsive solid substrates and/or overlying liquids can allow active control through induced temperature gradients, electrical stimulation, and exposure to magnetic fields. Recent work leveraging other advantages of liquid-infused systems such as ultra-low friction, noncoalescence of droplets, and liquid–liquid patterning has demonstrated the unique ways in which this approach can be used to both enhance current detection methods as well as enable new ones. Together, these recent developments in the manipulation of droplets on liquid-infused surfaces point to their significant potential for furthering the capacity of PON devices for both biological and environmental samples.