Biosorption of heavy metal ions by immobilized zoogloea and zooglan

ImmobilizedZoogloea and zooglan in calcium alginate-silica matrix was shown to have a high adsorption capacity for Cu and Cd ions. Our results showed that Cu-ion uptake in the presence of Ca and Mg ions can be enhanced using immobilizedZoogloea and zooglan. Heavy metal ion adsorption efficiency decreased in the following order: Cu > Cd > Zn > Cr. The adsorbed metal ions were desorbed completely using sulfuric acid. ImmobilizedZoogloea and zooglan which was repetitively regenerated adsorbed heavy metal ions without a loss of adsorption capacity.     

Self-assembly of asymmetric fan-shaped dendrimers with different generation numbers at the air-water interface

Monolayer formation of two dendrimers containing a hydrophilic core group (COOH) and hydrophobic peripheral groups (anthracene and aryl ether tail groups), 4-{10-[4-(3,5-bis-benzyloxy)-phenyl]-anthracen-9-yl}-benzoic acid (G1) and 4-(10-{4-[3,5-bis-(3,5-bis-benzyloxy)-benzyloxy]-phenyl}-anthracen-9-yl)-benzoic acid (G2), were studied. To understand the mechanism of the self-assembly of these molecules, we measured the surface pressure-surface area (Pi- A) isotherm and investigated the surface texture of Langmuir-Blodgett monolayers transferred onto hydrophilic silicon wafers. Both dendrimers form circular domains at the onset point of surface pressure as a result of the difference in hydrophobicity between the core group and the peripheral end group. The core group has a functional group at the end of dendrimer and can be anchored on the water surface. Upon further compression, monolayer of G1 shows a domain of molecules whereas a monolayer of G2 is aligned in the direction of compression at 10 mN/m. At higher surface pressure (20 mN/m), G1 molecules have several aggregates of domains, but G2 molecules maintain their ordering. These results were confirmed by the electron density profile of G1 and G2 monolayers transferred to silicon substrates, as measured by X-ray reflectivity.     

Structure formation of hydrophobically end-capped poly(ethylene oxide) in the solid state

The conformational transition of hydrophobically end-capped poly(ethylene oxide), HP-PEO-HP [hydrophobic-poly(ethylene oxide)-hydrophobic], was studied using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) methods. Conformational transitions of HP-PEO-HP from a planar zigzag to a 7/2 helical conformation were observed as the molecular weight of the PEO main chain increased. HP-PEO-HP 1(18), with a PEO molecular weight of 1000 and 18 hydrocarbons on each end, has mainly an alpha-helical structure in poor solvents, whereas alpha and beta conformations coexist in good solvents. This means that the alpha-helical structure caused by the hydrogen bonds between the urethane linkages was broken by the high chain mobility caused by the melted adjacent chains of PEO, and instead, the beta-sheet was formed by the interaction of multiple hydrogen bonds. Another indication of hydrogen bonds breaking at increasing temperature is the transition of the N-H stretching peak in the FTIR data. HP-PEO-HP 2(18) and 4(18), which have 18 hydrocarbons on each end and PEO molecular weights of 2000 and 4000, respectively, and consist mostly of PEO, showed spherulites. This result also suggests that the PEO molecule has a 7/2 zigzag helical conformation. In contrast, HP-PEO-HP 1(18), which is composed of less PEO than HP-PEO-HP 2(18) and 4(18), did not show a spherulite structure.     

Dual mechanism for an online retailer

While posted price and auction have typically been seen as alternatives to each other, we observe Web stores selling a product at a posted price and simultaneously running auctions for the identical product, a phenomenon that has not been studied fully. In this article, we study a dual mechanism, where an online retailer combines the two conventional mechanisms (posted price and auction) for multiple units of a product. We demonstrate that the dual mechanism can be used to achieve market segmentation when customers discount the expected utility of auctions. We characterize the customer’s decision rule and formulate a retailer’s profit function under the dual mechanism. Finally, we compare the performance of three selling mechanisms (posted price, auction, and dual) through computational experiments.     

Evaluation of Efficiency of Polymerization,Surface Roughness,Porosity and Adaptation of Flowable and Sculptable Bulk Fill Composite Resins

A new category of commercial bulk fill composite resins (CRs) enables the placement of 4-mm-thick layers as an alternative to the traditional time-consuming incremental technique. The purpose of the present study was to compare the efficiency of the polymerization, adaptation and porosity of two high-viscosity ‘sculptable’ bulk fill CRs (Filtek™ Bulk Fill (3M™ ESPE, St. Paul, MN, USA) and Tetric EvoCeram^® Bulk Fill (Ivoclar Vivadent AG, Schwan, Liechtenstein)) and two low-viscosity ‘flowable’ bulk fill CRs (SureFil^® SDR™ flow (Dentsply Sirona, Charlotte, NC, USA) and Tetric EvoFlow^® Bulk Fill (Ivoclar Vivadent AG, Schaan, Liechtenstein)). Cylindrical samples of the bulk fill CRs (4 mm height × 10 mm diameter) were analyzed by Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Additionally, occlusal cavities were prepared in twelve extracted human molars and restored with the bulk fill CRs (n = 3 for each CR). The adaptation and porosity of the bulk fill CRs were evaluated by X-ray microcomputed tomography (µCT) with a 3D morphometric analysis, and the adaptation was also analyzed by scanning electron microscopy (SEM) on longitudinal vestibulo-oral sections of the restored teeth. The AFM analysis demonstrated that the surface roughness of the SureFil^® SDR™ flow was higher than that of the Tetric EvoFlow^® Bulk Fill and that the surface roughness of Filtek™ Bulk Fill was higher than that of Tetric EvoCeram^® Bulk Fill. µCT and SEM confirmed that the flowable bulk fill CRs had excellent adaptation to the cavity walls. The 3D morphometric analysis showed the highest and lowest degrees of porosity in Filtek™ Bulk Fill and Tetric EvoFlow^® Bulk Fill, respectively. In general, the flowable bulk fill CRs exhibited better adaptation, a higher efficiency of polymerization and lower porosity than the sculptable materials.     

Antiviral and Antibacterial Polyurethanes of Various Modalities

We have prepared and characterized a new polyurethane-based antimicrobial material, N,N-dodecyl,methyl-polyurethane (Quat-12-PU). It exhibits strong antiviral and antibacterial activities when coated (as an organic solution or an aqueous nanosuspension) onto surfaces and antibacterial activity when electrospun into nanofibers. Quat-12-PU surfaces are able to kill airborne Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria, as well as inactivate the enveloped influenza virus (but not the non-enveloped poliovirus).