Duplex strand formation using alternating copolymers

The regular arrangement of complementary diaminopyridine-thymine (DAP-THY) on alternating copolymers permits cooperative binding events and the effective formation of well-controlled micrometre-scale aggregates.     

Some low-modulus birefringent resins

Information is given to enable the photoelastician to select and prepare his own clear, bubblefree, constant-thickness, low-modulus (500 psi or less) birefringent resins. Various urethane formulations are examined. The effects of environment, mixing, casting, molds, cure, post-cure and calibration are discussed. A procedure to select a particular formulation is suggested.     

Coloured coatings containing mixed transition metal oxides

Glass coloured coatings of M_nO_m---N_pO_q---SiO₂ (M, N = Fe, Co, Ni, Mn, Cr) prepared on soda-lime-silica flat glasses by the sol-gel route using the dip-coating technique.

The optical properties of these films were investigated by spectrophotometry and the optical parameters obtained allowed the colouration mechanism acting in each case to be determined as well as a comparison to be made with the parameters on the single TMO coloured films. Colour coordinates were calculated in every case.

On the other hand coatings have been prepared consisting of two different single TMO films. The corresponding mixed coatings were compared with these double films, showing different behaviours and widening the colour spectrum of glass TMO coatings.     

PolyGuanine methacrylate cryogels for ribonucleic acid purification

The isolation and purification of ribonucleic acid have attracted attention recently for the understanding of the functions in detail because of the necessity for the treatment of genetic diseases. In this study, guanine‐incorporated polymeric cryogels were developed to obtain highly purified ribonucleic acid. The satisfactory purification performance was achieved with the guanine‐incorporated poly (2‐hydroxyethyl methacrylate‐guanine methacrylate) cryogels. The most crucial advantages to use guanine as a functional monomer are to obtain a real natural interaction between guanine on the polymeric material and cytosine on the ribonucleic acid. Moreover, using cryogel with a highly porous structure and high swelling ratio provide advantages of getting more water within the structure to get more analyte to interact. The characterization of cryogels has proved the success of the synthesis and the perfect natural interaction to be taken place between the ligand (guanine methacrylate) and the cytosine in the ribonucleic acid molecules. Although the pores within the structure of cryogels are small, they provide efficient and fast adsorption. The chromatographic separation performance was investigated for different conditions (pH, temperature etc.). The desorption ratio and reusability were also analyzed at the end of the five adsorption–desorption cycles with no significant changes.     

Study by grazing incident diffraction and surface spectroscopy of amalgams from ancient mirrors

Characterization of four amalgam surfaces, with different alteration degrees from Andalusia historical mirrors, has been carried out by grazing-incidence X-ray diffraction (GIXRD), and other spectroscopic techniques (SEM/EDX, XPS, and REELS). The combination of all these techniques allows determining the corrosion state of the amalgams. The results show that the amalgams are composed in all cases of a binary alloy of tin and mercury. As mercury has high vapour pressure at RT, it slowly segregates and eventually evaporates, it leaves finely divided particles of tin that easily can be oxidize, forming tin monoxide (SnO) and tin dioxide (SnO₂). In one of the samples, most of the amalgam remains unoxidized, since Hg_0.1Sn_0.9 and metallic Sn phases are the major components; in two other samples, Hg_0.1Sn_0.9 and Sn phases are not detected while SnO₂ and SnO phases appear. Finally, in the last studied sample, only SnO₂ phase is detected. The surface analyses of these samples by XPS show that, for most of them an unique chemical species (Sn⁴⁺) is found.      

Dynamic switching times from season to single tickets in sports and entertainment

Revenue management can be used in many industries where there is a limited, perishable capacity and the market can be segmented. In this paper we focus on the sales of event tickets in the Sports and Entertainment industries, where tickets are sold exclusively as season tickets initially or as single events later in the selling horizon. We specifically study the optimal time to switch between these market segments dynamically as a function of the state of the system. Under Poisson demand processes, we find the optimal switching time is a set of time thresholds that depends on the remaining inventory and time left in the horizon. We use numerical experiments to show that significant profit improvements can be obtained by dynamically deciding the optimal switch time over the case when the date is announced in advance. We also study an extension where ??early switch to a low-demand event?? is allowed.     

Synthesis of Boltorn 1,2,3‐triazole dendrimers by click chemistry

Second‐, third‐, and fourth‐generation hyperbranched aliphatic polyols namely Boltorn® H20, Boltorn H30, and Boltorn H40 were endcapped with azido and activated acetylenic groups in good to excellent yields (75–95%) following an acid catalyzed procedure. The resultant terminally functionalized dendritic azido and acetylenic groups undergo 1,3‐dipolar cycloaddition using methyl (or ethyl) propiolate and benzyl azide, respectively, under catalytic or noncatalytic conditions below 40 °C to yield 1,2,3‐triazole dendrimeric polymers in 82–95% yield, under extremely mild conditions that could be applied for compounds sensitive to acid, base, or heat. The dendritic azido and activated acetylenic derivatives may act as novel scaffolds to tune the mechanical properties of different polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3748–3756, 2009     

Nanometric thin films of non-doped diamond-like carbon grown on n-type (P-doped) silicon substrates as electrochemical electrodes

Journal of Solid State Electrochemistry - The electrochemical response of thin non-doped diamond-like carbon films grown by pulsed laser deposition onto n-type (P-doped) silicon substrates was...     

Ratio asymptotics and quadrature formulas

A technique to find the asymptotic behavior of the ratio between a polynomialss _n and thenth orthonormal polynomial with respect to a positive measureμ is shown. Using it, some new results are found and a very simple proof for other classics is given.     

Comparison of the AIM delocalization index and the Mayer and fuzzy atom bond orders

In this paper the behavior of three well-known electron-sharing indexes, namely, the AIM delocalization index and the Mayer and fuzzy atom bond orders are studied at the Hartree-Fock level. A large number of five-membered ring molecules, containing several types of bonding, constitute the training set chosen for such purpose. A detailed analysis of the results obtained shows that the three indexes studied exhibit strong correlations, especially for homonuclear bonds. The correlation is somewhat poorer but still significant for polar bonds. In this case, the bond orders obtained with the Mayer and fuzzy atom approaches are normally closer to the formally predicted bond orders than those given by the AIM delocalization indexes, which are usually smaller than those expected from chemical intuition. In some particular cases, the use of diffuse functions in the calculation of Mayer bond orders leads to unrealistic results. In particular, noticeable trends are found for C-C bonds, encouraging the substitution of the delocalization index by the cheaper fuzzy atom or even the Mayer bond orders in the calculation of aromaticity indexes based on the delocalization index such as the para-delocalization index and the aromatic fluctuation index.