Synthesis of silica hybrid nanoparticles modified with photofunctional polymers and construction of colloidal crystals

Photofunctional polymer as silane coupling agent (PFD) was prepared by free radical copolymerization of 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC) and methyl methacrylate (MMA) in the presence of (3‐mercaptopropyl)trimethoxysilane (MPMS) as chain transfer agent. Next, silane (SiO₂; the average diameter D_n = 192 nm) nanoparticles was surface‐modified with PFD and 3‐(trimethoxysilyl)propyl methacrylate (γ‐MPS) by covalent bond formed between silanol groups and silane coupling agents. The PFD and γ‐MPS functionalizations changed the silica surface into hydrophobic nature and provided grafting initiation sites and methacrylate terminal groups respectively. We performed the construction of hybrid nanocomposites by using these modified SiO₂ nanoparticles. It was found from electron microscopy observations that SiO₂ particles were packed into repeating cubic arrangements in a poly(methyl methacrylate) (PMMA) matrix such as colloidal crystals. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Are Gaussian spectra a viable perceptual assumption in color appearance?

Natural illuminant and reflectance spectra can be roughly approximated by a linear model with as few as three basis functions, and this has suggested that the visual system might construct a linear representation of the spectra by estimating the weights of these functions. However, such models do not accommodate nonlinearities in color appearance, such as the Abney effect. Previously, we found that these nonlinearities are qualitatively consistent with a perceptual inference that stimulus spectra are instead roughly Gaussian, with the hue tied to the inferred centroid of the spectrum [J. Vision 6(9), 12 (2006)]. Here, we examined to what extent a Gaussian inference provides a sufficient approximation of natural color signals. Reflectance and illuminant spectra from a wide set of databases were analyzed to test how well the curves could be fit by either a simple Gaussian with three parameters (amplitude, peak wavelength, and standard deviation) versus the first three principal component analysis components of standard linear models. The resulting Gaussian fits were comparable to linear models with the same degrees of freedom, suggesting that the Gaussian model could provide a plausible perceptual assumption about stimulus spectra for a trichromatic visual system.     

Contrast adaptation reveals increased organizational complexity of chromatic processing in the visual evoked potential

Results from psychophysics and single-unit recordings suggest that color vision comprises multiple stages of processing. Postreceptoral channels appear to consist of both a stage of broadly tuned opponent channels that compare cone signals and a subsequent stage, which includes cells tuned to many different directions in color space. The chromatic visual evoked potential (crVEP) has demonstrated chromatic processing selective for cardinal axes of color space. However, crVEP evidence for higher-order color mechanisms is lacking. The present study aimed to assess the contribution of lower- and higher-order color mechanisms to the crVEP by using chromatic contrast adaptation. The results reveal the presence of mechanisms tuned to intermediate directions in color space in addition to those tuned to the fundamental cardinal axes.     

Tests of a functional account of the Abney effect

The Abney effect refers to changes in the hue of lights as they are desaturated. Normally the purity is varied by desaturating with a ?xed spectrum. Mizokami et al. [J. Vis.6, 996 (2006)] instead varied purity by using Gaussian spectra and increasing their bandwidth. Under these conditions the hues of lights at short and medium wavelengths tended to remain constant and thus were tied to a ?xed property of the stimulus such as the spectral peak, possibly reflecting a compensation for the spectral filtering effects of the eye. Here we test this account more completely by comparing constant hue loci across a wide range of wavelengths and between the fovea and periphery. Purity was varied by adding either a ?xed spectrum or by varying the spectral bandwidth, using an Agile Light Source capable of generating arbitrary spectra. For both types of spectra, hue loci were approximated by the Gaussian model at short and medium wavelengths, though the model failed to predict the precise form of the hue changes or the differences between the fovea and periphery. Our results suggest that a Gaussian model provides a useful heuristic for predicting constant hue loci and the form of the Abney effect at short and medium wavelengths and may approximate the inferences underlying the representation of hue in the visual system.     

Phosphorylation of ovalbumin by dry-heating in the presence of pyrophosphate: Effect of carbohydrate chain on the phosphorylation level and heat stability

Ovalbumin (OVA) derived from egg white (N-OVA) and recombinant OVA (Re-OVA), which was essentially carbohydrate-free, expressed by Escherichia coli, were phosphorylated by dry-heating for 1 day in the presence of pyrophosphate (PP-N- and PP-Re-OVA). The phosphorus contents of N- and Re-OVA were 0.79% and 0.46%, respectively, after phosphorylation. The secondary structural change of both OVAs was small, and the midpoint temperature of both OVAs determined from the thermal unfolding curve was decreased by phosphorylation. In addition, the differential scanning calorimetry thermograms of both OVAs showed a lowering of denaturation temperature by phosphorylation. The stability of both OVA solutions after heating at pH 7.0 was improved, and the degree of stabilization was higher for PP-N-OVA than for PP-Re-OVA. This suggests that the phosphate groups introduced to the carbohydrate chain also play an important role in the heat stability of OVA.     

Absolute quantitation of quercetin and the glycosides in natural food additives by quantitative NMR

We are developing a simple absolute quantitation method for organic compounds, by means of quantitative nuclear magnetic resonance (qNMR), with traceability to the International System of Units (SI units). The qNMR method was applied to the absolute quantitation of rutin, isoquercitrin and quercetin in natural food additives, rutin (extract), enzymatically decomposed rutin extract and quercetin, and those compounds as commercial reagents. In this study, 1,4-bis-(trimethylsilyl)benzene-d(4) (1,4-BTMSB-d(4)) whose purity was precisely evaluated on the basis of metrology, was newly used as a qNMR reference material, to be added to the sample solution as an internal standard. The contents of quercetin and quercetin glycosides were calculated from the ratio of the signal intensities of each aromatic proton at the 2' position of the three compounds (these are observed at different chemical shifts) to the eighteen protons of the six methyl groups on 1,4-BTMSB-d(4) used as a qNMR reference material. Rapid and simple qNMR method with only one step process was carried by using 1,4-BTMSB-d(4). It was demonstrated that the purities of rutin, isoquercitrin and quercetin can be separately determined by qNMR without the need for a separation process or reference materials for all the target compounds.     

Leaching of Lead and Connectivity of Plumbate Networks in Lead Silicate Glasses

The formation of a plumbate network in binary lead silicate glasses was examined based on the leaching behavior of Pb²⁺ in lead silicate glasses over a wide composition region. The effective diffusion coefficient of Pb²⁺ at 40°C was on the order of 10⁻¹⁷ m²/s for PbO<35 mol% glasses, and increased three orders of magnitude for 35–50 mol% PbO contents. Such a steep composition dependence is considered to be because of changes in the medium or longer range structure. That is, it is proposed that the plumbate network forms a percolative 3D network in the composition region to form diffusion paths for the lead ions. In addition, the present results indicate that the lead ion exists as a network former over the entire glass forming composition range of the binary silicate glasses.     

Molecular mechanics and molecular orbital simulations on specific interactions between peroxisome proliferator-activated receptor PPARalpha and plasticizer

Peroxisome proliferator-activated receptor α (PPARα) has various physiological functions such as lipid and glucose metabolism, inflammation and fibrosis in living organisms. Many types of ligand molecules such as phthalate and adipate esters control these physiological functions. In the present study, to elucidate the dependence of PPARα properties on ligand binding, we investigated stable structures and electronic properties for the complexes of PPARα and phthalate as well as adipate esters, which are used as a plasticizer, by molecular simulations based on molecular mechanics and molecular orbital methods. Furthermore, to elucidate the influence of these esters in vivo, we injected them into male mice and observed the change in the expression of PPARα-related enzymes. The comparison between the calculated and observed results indicates that the change in the expression has a correlation with the size of energy gaps between highest occupied and lowest unoccupied molecular orbitals of the complexes with mouse PPARα and esters.