Bactericidal performance of photocatalytic titanium dioxide particle mixture under ultraviolet and fluorescent light: an in vitro study

When ultraviolet (UV) light comes into contact with titanium dioxide (TiO₂), a variety of free radicals are released to provide a potent oxidizing power. Few reports are available, however, evaluating the bactericidal effects of TiO₂ particle under UV light and fluorescent light (FL) in the same line of research for clinical applications. In the present study, we set out to evaluate the in vitro photocatalytic bactericidal effects on Staphylococcus aureus, which is one of the most common pathogens of infectious disease, in an aqueous system of TiO₂ particles irradiated by UV and FL. A TiO₂ particle mixture containing 0.019 mg/ml of TiO₂ was prepared. A bacterial solution was added dropwise to the mixture, and the resulting product was irradiated by UV or FL light. The colony‐forming units were counted and the bacterial survival rate was calculated. Control samples maintained a relatively high bacterial survival rate. In the TiO₂ mixture group, however, the bacterial survival rate decreased steadily, reaching 9.4% after 60 min of exposure to UV light and 10.9% after 60 min of FL irradiation. Distributing the TiO₂ particles in a water mixture produces highly efficient light absorption and enables greater and more frequent adhesion with bacteria, allowing a high degree of photocatalytic antibacterial action. Although the quantity was inferior to UV, our TiO₂ particles were able to show effective bactericidal activity even under FL. The TiO₂ particle mixture is expected to prove effective in preventing postoperative infection. Copyright © 2009 John Wiley & Sons, Ltd.     

An Assmus–Mattson theorem for codes over commutative association schemes

We prove an Assmus–Mattson-type theorem for block codes where the alphabet is the vertex set of a commutative association scheme (say, with s classes). This in particular generalizes the Assmus–Mattson-type theorems for \(\mathbb {Z}_4\)-linear codes due to Tanabe (Des Codes Cryptogr 30:169–185, 2003) and Shin et al. (Des Codes Cryptogr 31:75–92, 2004), as well as the original theorem by Assmus and Mattson (J Comb Theory 6:122–151, 1969). The weights of a code are s-tuples of non-negative integers in this case, and the conditions in our theorem for obtaining t-designs from the code involve concepts from polynomial interpolation in s variables. The Terwilliger algebra is the main tool to establish our results.     

Investigation of Gold Quantum Dot Enhanced Organic Thin Film Solar Cells

Gold quantum dots (AuQDs) are employed as photosensitizers in organic thin‐film solar cells (OSCs) to improve their photoelectric conversion properties. Three types of AuQDs with different fluorescence emission wavelengths are used: blue (B‐AuQDs), green (G‐AuQDs), and red (R‐AuQDs). AuQDs are loaded into the poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) thin‐film layer of OSCs. UV–vis spectra, atomic force microscope images, current density–voltage characteristics, and impedance spectra of the fabricated devices are measured for the three aforementioned types of AuQDs. All types of AuQDs improve the photoelectric conversion properties, and the G‐AuQD‐loaded OSCs exhibit the best improvement, exhibiting an efficiency increase of 10% compared with OSCs without the AuQDs. The fluorescence/photosensitization of the AuQDs plays an important role in the enhancement of the OSCs. Finite‐difference time‐domain simulations indicate increased electric field intensity due to a small degree of AuQDs aggregation.     

Identification of Glycyrrhiza species by direct analysis in real time mass spectrometry

DART (Direct Analysis in Real Time)-MS is a novel mass spectrometric ion source, and allows the analysis of most compounds at ambient pressure and ground potential by producing [M+H]+ molecular ion species. Using this method, we examined the compounds characteristic of several kinds of licorices. For the analysis of Glycyrrhiza inflata Batalin, the peak at m/z 339 originates mainly from [M+H]+ of licochalcone A (LA), a species-specific compound. This peak was hardly detected in G. glabra Linné and G. uralensis Fischer. These results indicate that G. inflata can be differentiated from the other two species by detection of LA peaks using DART-MS analysis.     

Investigation of interaction of Leu-enkephalin with lipid membranes

Enkephalins are peptides with morphine-like activity. To achieve their biological function, they must be transported from an aqueous phase to the lipid-rich environment of their membrane bound receptor proteins. In our study, zeta potential (ZP) method was used to detect the association of Leu-enkephalin and Leu-enkephalinamide with phospholipid liposomes constituted from egg-phosphatidylcholine (EPC), dioleoyl-phosphatidylethanolamine (DOPE), cholesterol (Chol), sphingomyelin (SM) as well as soybean phospholipid (SBPL). Transfer of the peptides over lipid membranes was examined by electrophysiology technique (ET) and fluorescence spectroscopy (FS), and further confirmed using 4-fluoro-7-nitrobenzofurazan (NBD-F) labeled Leu-enkephalin (NBD-F-enkephalin) with confocal laser scanning microscopy method (CLSM). Results of zeta potential showed that enkephalinamide associated with lipid membranes and gradually saturated on the membranes either hydrophobically or electrostatically or both. Data from electrophysiology technique indicated that Leu-enkephalin could cause transmembrane currents, suggesting the transfer of peptides across lipid membranes. Transfer examined by fluorescence spectroscopy implied that it could be separated into three steps, adsorption, transportation and desorption, which was afterward reaffirmed by confocal laser scanning microscopy. Transfer efficiencies of enkephalin across SBPL, EPC/DOPE, EPC/DOPE/SM, EPC/SM and EPC/Chol lipid bilayer membranes were evaluated with ET and CLSM experiments. Results showed that the addition of either sphingomyelin or cholesterol, or negatively charged lipid in lipid membrane composition could lower the transfer efficiency.     

Anomalous enhancement of a single high-order harmonic by using a laser-ablation tin plume at 47 nm

We have successfully demonstrated intensity enhancement of a single high-order harmonic at a wavelength of 46.76 nm by using low-ionized tin ions in a laser-ablation plume as the nonlinear medium. The ablation plume was produced by irradiating a solid tin target with a 10 mJ energy picosecond laser pulse. Strong 17th-harmonic generation at a wavelength of 46.76 nm was observed with a conversion efficiency of about 10(-4). We attribute the strong enhancement of the single high-order harmonic to multiphoton resonance with a strong radiative transition of the Sn II ion.     

Observation of anomalous diffusion in excised tissue by characterizing the diffusion-time dependence of the MR signal

This report introduces a novel method to characterize the diffusion-time dependence of the diffusion-weighted magnetic resonance (MR) signal in biological tissues. The approach utilizes the theory of diffusion in disordered media where two parameters, the random walk dimension and the spectral dimension, describe the evolution of the average propagators obtained from q-space MR experiments. These parameters were estimated, using several schemes, on diffusion MR spectroscopy data obtained from human red blood cell ghosts and nervous tissue autopsy samples. The experiments demonstrated that water diffusion in human tissue is anomalous, where the mean-square displacements vary slower than linearly with diffusion time. These observations are consistent with a fractal microstructure for human tissues. Differences observed between healthy human nervous tissue and glioblastoma samples suggest that the proposed methodology may provide a novel, clinically useful form of diffusion MR contrast.     

Emergent reaction-diffusion phenomena in capillary tubes

Pattern formation in the Belousov-Zhabotinsky reaction experiments carried out by filling capillary glass tubes with catalyst-immobilized gel for the reaction is reported. Under unperturbed and oscillatory conditions, helicoidal waves appear spontaneously. Quantitative structural data of those helices are obtained by devising an optical tomography technique for extracting rotationally symmetric structures from time-lapse data. Space-time representation of the catalyst oxidation reveals wave transmission phenomenon that is studied further by numerical simulations of a reduced spatial model.     

Colloidal aggregation in a nematic liquid crystal: topological arrest of particles by a single-stroke disclination line

We numerically study many-body interactions among colloidal particles suspended in a nematic liquid crystal, using a fluid particle dynamics method, which properly incorporates dynamical coupling among particles, nematic orientation, and flow field. Based on simulation results, we propose a new type of interparticle interaction in addition to well-known quadrupolar interaction for particles accompanying Saturn-ring defects. This interaction is mediated by the defect of the nematic phase: upon nematic ordering, a closed disclination loop binds more than two particles to form a sheetlike dynamically arrested structure. The interaction depends upon the topology of a disclination loop binding particles, which is determined by aggregation history.