A method for selective isolation and aggregation of epicuticular wax nanotubes in Picea pungens

A method for selectively isolating and aggregating intact nanotubes from leaf surfaces, in sample quantities useable for their characterisation in further experimental investigations, is presented here. It uses liquid sucrose, as a saturated solution, with its wetting behaviour modified by the addition of controlled amounts of ethanol, as a temporary entrapment and release medium, for removing nanotube material from the leaf surface, here of Picea pungens (Engelmann). This harvesting technique works by the slow, gentle transition of the medium from liquid to solid, capturing the nanotubes, and then back to liquid again, releasing them, to form an aggregate sample, with little compromise to the structural integrity of individual nanotubes. Scanning electron microscopy (SEM) images are presented rigorously illustrating the technique and its effectiveness. Comparison with other recent methods reveals its advantages, and potential applications are explored.     

一类个体寿命有限的纯生过程

讨论了一类个体的寿命有限且一生分为若干个阶段的纯生过程 （ｐｕｒｅ ｂｉｒｔｈ ｐｒｏ－ｃｅｓｓ），其中每个阶段的存活率，繁殖率，其繁殖符合 Ｐｏｉｓｓｏｎ过程．证明了其小群体的繁衍分布服从分布；ｉ和ｊ两个不同阶段繁殖的时间间隔之比的密度函数为Ｆｉｂｏｎａｃｃｉ过程［４］中总体的期望数和寿命与指数分布有关等性质．     

Optical resolution of two isomeric naphthylalanines by immobilized enyzmes

Optical resolution of β-(1-naphthyl)alanine and β-(2-naphthyl)alanine have been efficiently carried out through enzymatic hydrolysis of their methyl ester and/or N-acetyl ester derivatives by immobilized enzymes. Difficulties related to the lipophilic character of these amino acids were overcome by using emulsions of n-butyl acetate–water as reaction medium. The use of an automatic recirculating apparatus allowed reproducible and repetitive use of the immobilized biocatalysts.     

Dynamical heterogeneity and anomalously dynamical slowdown in liquid alumina

Molecular dynamics simulations of liquid alumina with various temperatures ranging from 2400 to 4000 K were carried out to investigate dynamical properties. The evolution of structural AlO_x units (where x = 3–6) for different times were examined. We have also traced the time evolution of breakage and formation of AlO_x units in the cluster of 30 neighbouring AlO_x units. The simulation shows that AlO₄ units link together to form the clusters and AlO₅ units are connected to form the poly-units expanding all over the network structure. Dynamical heterogeneity in liquid alumina is caused by less mobile regions containing clusters of AlO₄ units and more mobile regions containing major AlO₅ units. The diffusivity of the aluminium atom is realised through the AlO_x ? AlO_x+1 transition. We also found that the dynamical slowdown in liquid alumina is determined by two terms: The first one relates to the frequency of AlO_x ? AlO_x+1 transitions and the second term mainly relates to the spatial arrangement of AlO_x ? AlO_x+1 transitions. The investigation reveals that the anomalously slow dynamics near the melting temperature is mainly caused by the localisation of AlO_x ? AlO_x+1 transitions.     

Alumina surfaces with nanoscale topography reduce attachment and biofilm formation by Escherichia coli and Listeria spp.

This work reports on a simple, robust and scientifically sound method to develop surfaces able to reduce microbial attachment and biofilm development, with possible applications in medicine, dentistry, food processing, or water treatment. Anodic surfaces with cylindrical nanopores 15 to 100 nm in diameter were manufactured and incubated with Escherichia coli ATCC 25922 and Listeria innocua. Surfaces with 15 and 25 nm pore diameters significantly repressed attachment and biofilm formation. Surface–bacteria interaction forces calculated using the extended Derjaguin Landau Verwey-Overbeek (XDLVO) theory indicate that reduction in attachment and biofilm formation is due to a synergy between electrostatic repulsion and surface effective free energy. An attachment study using E. coli K12 strains unable to express appendages also suggests that the small-pore surfaces may inhibit flagella-dependent attachment. These results can have immediate, far-reaching implications and commercial applications, with substantial benefits for human health and life.     

Synthesis of tritiated abscisic acid of high specific activity

Stable abscisic acid (RS)-[³H] was synthesized at a specific activity of 21 Ci/mmol using a basic alumina catalyzed proton exchange of 1-hydroxy-4-keto-α-ionone with T₂O followed by a Wittig reaction. Abscisic acid -[³H] of specific activity 102 mCi/mmol was synthesized after carrying out a base catalyzed tritium exchange in solution.     

Effect of heat treatment in vacuum on photoluminescence of anodic alumina

The results are presented of a study of the photoluminescent (PL) properties of an undoped porous anodic alumina (PAA) and PAA doped with manganese ions. The PAA samples were prepared by anodization of aluminum. The effect of annealing conditions in vacuum on the PL spectra was studied for the first time and a comparative analysis was made with the spectra of the PAA annealed in air. Vacuum annealing was used to obtain oxygen‐deficient alumina. A strong dependence of the PAA PL intensity on the annealing temperature in vacuum has been found: for the samples annealed at 600°С, the PL intensity is 15 times higher than that measured on the initial samples, whereas for the samples annealed in air it increases only 4.5‐fold with excitation at the wavelengths of 275 nm. This is the result of the formation of a high concentration of oxygen vacancies during annealing in vacuum under conditions of oxygen deficiency as compared with the samples annealed in air, where diffusion of oxygen from air leads to a decrease in vacancies. A significant increase in the PL intensity permits consideration of the vacuum‐annealed PAA as a promising material for dosimetry.     

Restriction-modification systems and bacteriophage invasion: Who wins?

The success of a phage that infects a bacterial cell possessing a restriction-modification (R-M) system depends on the activities of the host methyltransferase and restriction endonuclease, and the number of susceptible sites in the phage genome. However, there is no model describing this dependency and linking it to observable parameters such as the fraction of surviving cells under excess phage, or probability of plating at low amount of phages. We model the phage infection of a cell with a R-M system as a pure birth process with a killing state. We calculate the transitional probabilities and the stationary distribution for this process. We generalize the model developed for a single cell to the case of multiple identical cells invaded by a Poisson-distributed number of phages. The R-M enzyme activities are assumed to be constant, time-dependent, or random. The obtained results are used to estimate the ratio of the methyltransferase and endonuclease activities from the observed fraction of surviving cells.