Direct Electrochemistry of Glucose Oxidase at Carbon Nanotube‐gold Colloid Modified Electrode with Poly(diallyldimethylammonium chloride) Coating

Glucose oxidase showed direct electrochemical transfer at glassy carbon electrodes immobilized with carbon nanotube‐gold colloid (CNT‐Au) composites with poly(diallydimethylammonium chloride) (PDDA) coatings. The modified electrode (GC/CNT/Au/PDDA‐GOD) was employed for the amperometric determination of glucose. Under optimal conditions, the biosensor displayed linear response to glucose from 0.5 to 5 mM with a sensitivity of 2.50 mA M^?1 at an applied potential of ?0.3 V (vs. Ag|AgCl reference).     

Imaging the reaction dynamics of OH + CD4. 3. Isotope effects

Isotope effects in the reaction of hydroxyl radical with methane are investigated in a crossed-beam experiment. By exploiting different combinations of OH/OD + CH4/CD4/CHD3, a total of eight isotopically variant reactions are examined to decipher the dynamical consequence of both primary and secondary isotope effects. The most prominent observation is from isotopic substitution of the transferred atom (primary isotope effect), which yields more stretch-excited water product for the D atom case than H atom. The opposite is found, however, for excitations in bending and combination modes. The secondary isotope effects, from either substituted hydroxyl radical or the three H atoms that are not being abstracted, are relatively minor and manifest themselves in spreading the vibrational distribution of the water coproducts.     

Effect of complex formation on the half wave potentials of redox active ligands

A general equation is derived for the shift in half wave potential, ΔE , for ligand reduction on complexation with a metal. The formation of several complexes with differing stoichiometry and protonation states is considered explicitly. The dependence of ΔE on metal ion concentration, holding the ligand concentration constant, can be used to determine stability constants or their ratios. The meaning of ΔE depends on the stoichiometric changes following ligand oxidation state change, in a manner analogous to the case where the metal is the redox site.     

The Drude-Smith Equation and Related Equations for the Frequency-Dependent Electrical Conductivity of Materials: Insight from a Memory Function Formalism

The Drude-Smith equation is widely used for treating the frequency-dependent electrical conductivity of materials in the terahertz region. An attractive feature is its sparsity of adjustable parameters. A significant improvement over Drude theory for these materials, the theory includes backscattering of the charge carriers. It has nevertheless been criticized, including by Smith himself, because of the arbitrariness of a step in the derivation. We recall a somewhat similar behavior of back scattering in fluids observed in molecular dynamics computations and discussed in terms of memory functions. We show how theories such as Drude-Smith and Cocker et al. are examples of a broader class of theories by showing how they also arise as particular cases of a memory function formalism that divides the interactions into short and long range.     

Amphiphilic diblock copolymers based on poly(2‐ethyl‐2‐oxazoline) and poly(4‐substituted‐ε‐caprolactone): Synthesis,characterization, and cellular uptake

Amphiphilic diblock copolymers with various block compositions were synthesized on poly(2‐ethyl‐2‐oxazoline) (PEtOz) as a hydrophilic block and poly(4‐methyl‐ε‐caprolactone) (PMCL) or poly(4‐phenyl‐ε‐caprolactone) (PBCL) as a hydrophobic block. These PEtOz‐b‐PMCL and PEtOz‐b‐PBCL copolymers consisting of soft domains of amorphous PEtOz and PM(B)CL had no melting endothermal peaks but displayed T_g. The lower critical solution temperature (LCST) values for the PEtOz‐b‐PMCL, and the PEtOz‐b‐PBCL aqueous solution were observed to shift to lower temperature than PEtOz homopolymers. Their aqueous solutions were characterized using fluorescence techniques and dynamic light scattering (DLS). The block copolymers formed micelles with critical micelle concentrations (CMCs) in the range 0.6–11.1 mg L^?1 in an aqueous phase. As the length of the hydrophobic PMCL or PBCL blocks elongated, lower CMC values were generated. The mean diameters of the micelles were between 127 and 318 nm, with PDI in the range of 0.06–0.21, suggesting nearly monodisperse size distributions. The drug entrapment efficiency and drug‐loading content of micelles depend on block polymer compositions. In vitro cell viability assay showed that PEtOz‐b‐PMCL has low cytotoxicity. Doxorubicin hydrochloride (DOX)‐loaded micelles facilitated human cervical cancer (HeLa) cell uptake of DOX; uptake was completed within 2 h, and DOX was able to reach intracellular compartments and enter the nuclei by endocytosis. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2769–2781     

Excess molar enthalpies of binary systems containing 2-octanone,hexanoic acid,or octanoic acid at T = 298.15 K

An isothermal titration calorimeter was used to measure the excess molar enthalpies (H^E) of six binary systems at T = 298.15 K under atmospheric pressure. The systems investigated include (1-hexanol + 2-octanone), (1-octanol + 2-octanone), (1-hexanol + octanoic acid), (1-hexanol + hexanoic acid), {N,N-dimethylformamide (DMF) + hexanoic acid}, and {dimethyl sulfoxide (DMSO) + hexanoic acid}. The values of excess molar enthalpies are all positive except for the DMSO- and the DMF-containing systems. In the 1-hexanol with hexanoic acid or octanoic acid systems, the maximum values of H^E are located around the mole fraction of 0.4 of 1-hexanol, but the H^E vary nearly symmetrically with composition for other four systems. In addition to the modified Redlich–Kister and the NRTL models, the Peng–Robinson (PR) and the Patel–Teja (PT) equations of state were used to correlate the excess molar enthalpy data. The modified Redlich–Kister equation correlates the H^E data to within about experimental uncertainty. The calculated results from the PR and the PT are comparable. It is indicated that the overall average absolute relative deviations (AARD) of the excess enthalpy calculations are reduced from 18.8% and 18.8% to 6.6% and 7.0%, respectively, as the second adjustable binary interaction parameter, k_bij, is added in the PR and the PT equations. Also, the NRTL model correlates the H^E data to an overall AARD of 10.8% by using two adjustable model parameters.     

Formation of microporous poly(hydroxybutyric acid) membranes for culture of osteoblast and fibroblast

Microporous membranes of a biodegradable polymer, poly(hydroxybutyric acid) (PHB), were prepared by a phase‐inversion process and their cell compatibility was evaluated in vitro. A ternary system, ethanol/chloroform/PHB, was employed to prepare the membranes, wherein ethanol and chloroform were served as the nonsolvent and solvent for PHB, respectively. In the phase‐inversion process, the polymer dissolution temperature was varied from 80 to 120°C to yield membranes with specific morphologies, such as globular particles, porous channels, etc. Moreover, cell viability was examined on the formed membranes. Two cell lines, osteoblast hFOB1.19 and fibroblast L929, were cultured in vitro. It was found that these two types of cells exhibited different responses on different membranes: the hFOB1.19 cells showed significant increase in cell proliferation with increase in surface roughness, whereas the L929 cells demonstrated an opposite trend, preferring to attach and grow on a flat surface. PHB membranes with different morphologies exhibit different cell compatibilities, which may be useful means for the architectural design of materials for tissue engineering. Copyright © 2009 John Wiley & Sons, Ltd.     

Perception of urban park soundscape

A number of studies have been initiated to explore how to improve the soundscape quality in urban parks. However, good soundscape quality in parks cannot be provided without a thorough understanding of the complex relationships among sound, environment, and individuals. As acoustic comfort is considered to be an important outcome of soundscape quality, this study investigates the relative impacts of the factors influencing acoustic comfort evaluation by formulating a multivariate ordered logit model. This study also explores the inter-relationships among acoustic comfort evaluation, acceptability of the environment, and preference to stay in a park using a path model. A total of 595 valid responses were obtained from interview surveys administered in four parks in Hong Kong while objective sound measurements were carried out at the survey spots concurrently. The findings unveil that acoustic comfort evaluation, besides visual comfort evaluation of landscape, also plays an important role on users' acceptability of the urban park environment. Compared with all the studied acoustic related factors, acoustic comfort evaluation serves as a better proxy for park users' preference to stay in urban parks. Hearing the breeze will significantly increase the likelihood of individuals in giving high acoustic comfort evaluation. Conversely, hearing the sounds from heavy vehicles or sounds from bikes will significantly reduce the likelihood in giving a high acoustic evaluation.