Corneal Critical Barrier against the Penetration of Dexamethasone and Lomefloxacin Hydrochloride: Evaluation by the Activation Energy for Drug Partition and Diffusion in Cornea

The cornea is a solid barrier against drug permeation. We searched the critical barrier of corneal drug permeation using a hydrophobic drug, dexamethasone (DM), and a hydrophilic drug, lomefloxacin hydrochloride (LFLX). The activation energies for permeability of DM and LFLX across the intact cornea were 88.0 and 42.1 kJ/mol, respectively. Their activation energies for permeability across the cornea without epithelium decreased to 33.1 and 16.6 kJ/mol, respectively. The results show that epithelium is the critical barrier on the cornea against the permeation of a hydrophobic drug of DM as well as a hydrophilic drug of LFLX. The activation energy of partition for DM (66.8 kJ/mol) was approximately 3-fold larger than that of diffusion (21.2 kJ/mol). The results indicate that the partition for the hydrophobic drug of DM to the corneal epithelium is the primary barrier. Thermodynamic evaluation of activation energy for the drug permeation parameters is a good approch to investigate the mechanism of drug permeability.     

Thermal Behavior of Potato Starch and Water-Vaporization Behavior of Its Paste Controlled with Amino Acid and Peptide-Rich Food Materials

ABSTRACT: The particular effect of 4 kinds of amino acid and peptide-rich food material (APRM) containing different charged amino acid contents on the gelatinization and retrogradation behavior of potato starch granules and on the water-vaporization behavior was analyzed by differential scanning calorimetry, rapid viscoanalysis, x-ray diffractometry, thermal gravimetry-differential thermal analysis, and pulsed NMR. APRM with a high-charged amino acid content produced unique gelatinization and retrogradation behavior in terms of an elevated gelatinization temperature, reduced viscosity, higher setback, and lower retrograded starch melting enthalpy. The recovered x-ray diffraction intensity decreased with increasing charged amino acid content. APRM with high-charged amino acid content could provide an improved paste having easy vaporization of external water in the swollen starch granules due to the reduced swelling.     

Grain growth prediction based on data assimilation by implementing 4DVar on multi-phase-field model

We propose a method to predict grain growth based on data assimilation by using a four-dimensional variational method (4DVar). When implemented on a multi-phase-field model, the proposed method allows us to calculate the predicted grain structures and uncertainties in them that depend on the quality and quantity of the observational data. We confirm through numerical tests involving synthetic data that the proposed method correctly reproduces the true phase-field assumed in advance. Furthermore, it successfully quantifies uncertainties in the predicted grain structures, where such uncertainty quantifications provide valuable information to optimize the experimental design.     

Reliability-based design for earth-fill dams against severe natural disaster events

The maintenance of geotechnical structures, such as earth-fill dams, is required as a countermeasure against severe natural disasters, particularly earthquakes and heavy rains. The reliability-based analysis introduced here is in response to the recent demand for low-cost improvements.First, a statistical model of N values was determined from Swedish weight sounding (SWS) tests to present the spatial variability of the soil strength. Then, a reliability-based analysis of embankments was conducted by considering the variability of the internal friction angle derived from N value, and the seismic hazard for the Nankai Trough. The next step was to evaluate the probability of the overflow of earth-fills during heavy rains. The rainfall intensity was considered as a probabilistic parameter, and the various rainfall patterns were tested by the proposed method. Finally, the total risk due to both earthquakes and heavy rains was evaluated for an earth-fill site. As a result, the possibility for the practical use of the proposed method in making plans for the maintenance of deteriorated earth-fill dams was verified.     

Enhancement of oxygen reduction activity of nanoshell carbons by introducing nitrogen atoms from metal phthalocyanines

Nanoshell carbon is a type of catalytically grown nanocarbon with a hollow, round, shell-like structure, with a diameter in the range of approximately 20-50 nm. It has been shown to possess the electrocatalytic activity for oxygen reduction reaction (ORR) and is also expected to be a non-Pt catalyst for polymer electrolyte fuel cells. This paper reports the synergetic enhancement of the ORR activity of nanoshell carbons caused by the coexistence of nitrogen atoms. The nanoshell carbons were prepared by the carbonization of furan resin in the presence of acetylacetonates (AAs) and of phthalocyanines (Pcs), which contained Fe, Co, and Ni. The Pc-derived nanoshells (MP-T series; M = Co or Fe, T = carbonization temperature) showed higher ORR activities than the AA-derived nanoshells (MA-T series; M = Co or Fe, T = carbonization temperature) when the same metal elements were employed. An XPS study revealed that nitrogen species were introduced to the surface of the nanoshells when Pcs were used as the nanoshell-forming catalysts, and that no metal species remained on the nanoshells. Principally, the ORR activity of the carbons was governed by the presence of the nanoshells and further enhancement could be achieved by the introduction of nitrogen atoms. 0.78 V of OCV and 0.21 W cm⁻² of the maximum power density were observed for a fuel cell whose MEA consisted of 3CoP1000 cathode and a commercial Pt/C anode, when it was operated at 80 °C under a pressurized condition of 0.35 MPa.     

Remarkable difference of phase transition behaviors between Langmuir monolayers and aqueous bilayer vesicles of oligopeptide-carrying lipids

In this research, we synthesized six kinds of oligopeptide-carrying lipids which possessing glycine, diglycine, triglycine, alanine, dialanine, and trialanine residues (see Figure 1 for their formulae), and systematically investigated their phase transition behaviors both at the air-water interface and in aqueous bilayer vesicles. pi-A Isotherms of Langmuir monolayers of these lipids were measured at the air-water interfaces under varied temperature conditions and were analyzed based on compressibility of the monolayers. Above the specific temperature, the transition pressure from its expanded phase to condensed phase is not distinguishable with the collapse pressure of the monolayer, i.e., the monolayer collapses directly from the expanded phase without forming the condensed phase. This temperature was defined as the phase transition temperature of the monolayer, which was compared with the phase transition temperature of the corresponding bilayer vesicle in water. The phase transition temperatures of the oligoglycine-carrying lipids and oligoalanine-carrying lipids are significantly different at the air-water interface, while the corresponding difference is not obvious in their aqueous bilayer vesicles. Consideration based on molecular structures suggests necessity of the water mediation for effective formation of hydrogen bonding between the oligopeptide residues directly connected to dialkyl chains. Therefore, the differences in water accessibility to the films may cause the difference of the phase transition behaviors of the oligopeptide-carrying lipids between the Langmuir monolayers and the aqueous bilayer vesicles. Although the proposed mechanism is not fully supported by experimental evidences, the data presented here clearly demonstrated the presence of significant difference of the phase transition properties between the Langmuir monolayers at the air-water interface and aqueous bilayer vesicles of the oligopeptide-carrying lipids.     

Statistical data analysis method for multi-zonal airflow measurement using multiple kinds of perfluorocarbon tracer gas

Conventional multi-zonal ventilation measurement methods by multiple types of perfluorocarbon tracers use a number of different gases equal to the number of zones (n). The possible n×n+n airflows are estimated from the mass balance of the gases and the airflow balance. However, some airflows may not occur because of inter-zonal geometry, and the introduction of unnecessary, unknown parameters can impair the accuracy of the estimation. Also, various error factors often yield an irrational negative airflow rate. Conventional methods are insufficient for the evaluation of error. This study describes a way of using the least-squares technique to improve the precision of estimation and to evaluate reliability. From the equations’ residual, the error variance–covariance matrix Λ_q of the estimated airflow rate error is deduced. In addition, the coefficient of determinant using the residual sum of squares and total variation is introduced. Furthermore, the error matrix _mΛ_q from the measurement errors in the gas concentration and gas emission rate is deduced. The discrepancy ratio of the model premises is defined by dividing the diagonal elements of the former by those of the latter. Moreover, the index of irrationality of the estimated negative airflow rate is defined, based on the different results of the three estimation methods. Some numerical experiments are also carried out to verify the flow rate estimation and the reliability evaluation theory.     

Simple method for obtaining viscoelastic parameters of polymeric materials by incorporating physical-aging effects

A simple method for obtaining viscoelastic parameters from the results of static tensile tests is presented herein. Viscoelastic parameters were obtained by fitting experimental results and calculated results based on the power law model and linear viscoelasticity. The static tensile tests were carried out at various pre-aging times and the effect of physical aging was determined. The data confirmed that the physical aging process has a significant effect on the viscoelastic behavior. A creep test was conducted in order to discuss the validity of the prediction using the results of the static tensile test. It was confirmed that the predictions based on the viscoelastic parameters obtained from static tensile tests cannot adequately model actual viscoelastic behavior. The effective time theory was incorporated into the prediction in order to account for the progress of physical aging. It was verified that incorporating effective time theory into the prediction allows for the precise prediction of the long-term viscoelastic behavior.     

Prevalence and antimicrobial resistance of Salmonella in retail foods in northern China

A total of 387 retail meat, seafood and milk powder samples were collected from nine cities in northern China in 2005 and screened for the presence of Salmonella. Salmonella strains isolated were subjected to serotyping and antimicrobial susceptibility testing. Salmonella was isolated from 81 (20.9%, 81/387) samples and classified into 23 serotypes. The isolates were frequently resistant to sulfamethoxazole (86.4%), sulfamethoxazole/trimethoprim (48.1%), nalidixic acid (30.9%), tetracycline (19.8%), carboxybenzylpenicillin (17.3%), amoxicillin (17.3%) and ampicillin (16.0%). The multiple resistance (resistance to ≥ 3 antibiotics) was found in 29.6% (n = 24) isolates. Additionally, 4 isolates from chicken displayed the ACSSuTNx profile, resistant to ampicillin, chloramphenicol, streptomycin, sulfonamide, tetracycline and nalidixic acid, in particular, strain HBS084 showing the resistance to as many as 20 antibiotics. Salmonella from chicken showed the higher frequency of antimicrobial resistance. Our findings indicate that in northern China food products of animal origin can be a source of exposure for consumers to multiresistant Salmonella strains.     

Synthesis of Silicon Carbide Ceramics Using Chemically Modified Polycarbosilanes as a Compaction Binder

A chemically modified polycarbosilane (PC) containing organofluoric groups (PCOCF) has been synthesized from PC and fluoroalkylmethyldimethoxysilane. PCOCF acts as an efficient compaction binder for SiC powders and as a coating material with excellent oxidation resistance in wet air. PCOCF-coated SiC powders also show excellent packing properties because of the organofluoric side chains, which give highly dense green compacts. PCOCF provides a high ceramic yield of 75% and highly dense SiC ceramics. Four-point bending strength increases and the scatter in strength values decreases significantly by PCOCF coating.