Controlling chaos in dynamic-mode atomic force microscope

We successfully demonstrated the first experimental stabilization of irregular and non-periodic cantilever oscillation in the amplitude modulation atomic force microscopy using the time-delayed feedback control. A perturbation to cantilever excitation force stabilized an unstable periodic orbit associated with nonlinear cantilever dynamics. Instead of the typical piezoelectric excitation, the magnetic excitation was used for directly applying control force to the cantilever. The control force also suppressed the cantilever's occasional bouncing motions that caused artifacts on a surface image.     

Determination of REEs in seawater by ICP-MS after on-line preconcentration using a syringe-driven chelating column

A syringe-driven chelating column (SDCC) was applied to develop an on-line preconcentration/inductively coupled plasma mass spectrometry (ICP-MS) method for preconcentration and determination of rare earth elements (REEs) in seawater samples. The present on-line preconcentration system consists of only one pump, two valves, an SDCC, an ICP-MS, several connectors, and Teflon tubes. Optimizations of adsorption pH condition, sample loading flow rate, and integration range were carried out to achieve optimum measurement conditions for REEs in seawater sample. Six minutes was enough for a preconcentration and measurement cycle using 10 mL of seawater sample, where the detection limits for different REEs were in the range of 0.005 pg mL⁻¹ to 0.09 pg mL⁻¹. Analytical results of REEs in a seawater certified reference material (CRM), NASS-5, confirmed the usefulness of the present method. Furthermore, concentrations of REEs in Nikkawa Beach coastal seawater were determined and discussed with shale normalized REE distribution pattern.     

Peripherally Monomial-Preserving Maps between Uniform Algebras

Let and be uniform algebras and p(z,w) = z^mwⁿ a twovariable monomial. We characterize maps T from certain subsets of into such that holds for all f and g in the domain of T; peripherally monomial-preserving maps. Furthermore and are proved to be isometrical isomorphic as Banach algebras. If the greatest common divisor of m and n is 1, then T is extended to an isometrical linear isomorphism; a weighted composition operator. An example of peripherally monomial-preserving surjections between uniform algebras which is not linear, nor multiplicative, nor injective is given when the greatest common divisor is strictly greater than 1. The first, third and fourth authors were partly supported by the Grantsin-Aid for Scientific Research, The Ministry of Education, Science, Sports and Culture, Japan.     

Particle design of three-component system for sustained release using a 4-fluid nozzle spray-drying technique

We prepared composite particles of acetaminophen (Act) with chitosan (Cht) and hydroxypropylmethylcellulose phthalate (HPMCP) as a carrier using a newly developed 4-fluid nozzle spray-dryer. Cht dissolves in acid solutions and forms a gel, but it is insoluble in alkaline solutions. On the other hand, HPMCP is insoluble in acid solutions, but it dissolves in alkaline solutions. Therefore, we tested a preparation of controlled release composite particles using the characteristics of these carriers. Act and Cht mixtures in prescribed ratios were dissolved in an acid solution. Composite particles of Act and HPMCP in prescribed ratios were dissolved in alkaline solutions. We evaluated the composite particles of the three components (Act, Cht, and HPMCP) by preparing solid dispersions using a 4-fluid nozzle spray-dryer. Observation of particle morphology by scanning electron microscopy (SEM) revealed that the particles from the spray-drying process had atomized to several microns and had all become spherical. We investigated the physical properties of the composite particles by powder X-ray diffraction, differential scanning calorimetry, and dissolution rate analysis to clarify the effects of crystallinity on the dissolution rate. Powder X-ray diffraction peaks and the heat of fusion of Act in the spray-dried samples decreased in proportion to the carrier content, indicating that the drug was amorphous. These results indicate that the Act-Cht-HPMCP system formed a solid dispersion. Furthermore, we investigated the interaction between the drug and the carrier using FT-IR analysis. FT-IR spectroscopy of the Act solid dispersions suggested that the Act carbonyl and Cht amino groups formed a hydrogen bond. On the other hand, interaction by hydrogen bond was observed between the carbonyl group of HPMCP with the amino group of Act. In the three-component Act-Cht-HPMCP system, the 4-fluid nozzle spray-dried preparation with a mixing ratio of 1 : 2.5 : 2.5 obtained sustained release preparation in all pH test solutions.     

Particle design using a 4-fluid-nozzle spray-drying technique for sustained release of acetaminophen

We prepared matrix particles of acetaminophen (Act) with chitosan (Cht) as a carrier using a newly developed 4-fluid-nozzle spray dryer. Cht dissolves in acid solutions and forms a gel, but it does not dissolve in alkaline solutions. Therefore, we tested the preparation of controlled release matrix particles using the characteristics of this carrier. Act and Cht mixtures in prescribed ratios were dissolved in an acid solution. We evaluated the matrix particles by preparing a solid dispersion using a 4-fluid-nozzle spray dryer. Observation of the particle morphology by scanning electron microscopy (SEM) revealed that the particles from the spray drying process had atomized to several microns, and that they had become spherical. We investigated the physicochemical properties of the matrix particles by powder X-ray diffraction, differential scanning calorimetry, and dissolution rate analyses with a view to clarifying the effects of crystallinity on the dissolution rate. The powder X-ray diffraction peaks and the heat of the Act fusion in the spray-dried samples decreased with the increase of the carrier content, indicating that the drug was amorphous. These results indicate that the system formed a solid dispersion. Furthermore, we investigated the interaction between the drug and carrier using FT-IR analysis. The FT-IR spectroscopy for the Act solid dispersions suggested that the Act carboxyl group and the Cht amino group formed a hydrogen bond. In addition, the measurement results of the 13C CP/MAS solid-state NMR, indicated that a hydrogen bond had been formed between the Act carbonyl group and the Cht amino group. In the Act-Cht system, the 4-fluid-nozzle spray-dried preparation with a mixing ratio of 1 : 5 obtained a sustained release preparation in all pH test solutions.     

Sugar-dependent aggregation of glycoconjugated chlorins and its effect on photocytotoxicity in HeLa cells

In order to explore the influence of the sugar moieties of glycoconjugated chlorins on the photocytotoxicity, we studied the photochemical properties of four glycoconjugated chlorins in aqueous media such as cytoplasm and the concentration dependence of photocytotoxicity in HeLa cells. In phosphate-buffered saline, the fluorescence intensities of 5,10,15,20-tetrakis[3-(beta-D-glucopyranosyloxy)phenyl]chlorin (m-1a) and 5,10,15,20-tetrakis[3-(beta-D-galactopyranosyloxy)phenyl]chlorin (m-1b), i.e., chlorins having hexose groups, were about 2-fold greater than those of 5,10,15,20-tetrakis[3-(beta-d-xylopyranosyloxy)phenyl]chlorin (m-1c) and 5,10,15,20-tetrakis[3-(beta-d-arabinopyranosyloxy)phenyl]chlorin (m-1d), i.e., chlorins having pentose groups, owing to a sugar-dependent difference of aggregation behavior. While no cytotoxicity was found in the dark, the highest photocytotoxicity was shown by m-1a (82% inhibition) in HeLa cells. This was higher than those of m-1b, m-1c, m-1d and tetraphenylporphyrin tetrasulfonic acid. The glycoconjugated chlorins except for m-1b appeared to be distributed diffusely throughout the cytoplasm. Among the four photosensitizers, m-1a showed the highest intensity in confocal fluorescence images, in agreement with the in vitro photocytotoxicity results. For m-1c, no photocytotoxicity was found at drug concentrations from 0.2 to 0.04 microM. Hence, sugar-dependent aggregation is not the major reason for the unexpected lack of efficacy of m-1c, which is uptaken efficiently by HeLa cells. For the glycoconjugated chlorins, these results suggest the biological aspects of sugar moiety play much crucial role rather than chemical aspects.     

Photo-sensitive self-motion of a BQ disk

The photo-sensitive self-motion of a benzoquinone (BQ) disk was investigated on a hydroquinone (HQ) aqueous solution. The mode-switching of self-motion, i.e., continuous → intermittent → no motion, was observed with an increase in the concentration of HQ. Upon irradiation with UV light (～254 nm), the critical concentrations of HQ that were associated with the three modes of motion shifted to lower values, and the average speed of motion decreased. We discuss the mechanism of the photo-sensitive self-motion in relation to the photochemical reaction from BQ to HQ and the driving force of the disk.     

Altered posttranslational modification on U1 small nuclear ribonucleoprotein 68k in systemic autoimmune diseases detected by 2D Western blot

Anti-ribonucleoprotein (anti-RNP) antibodies are one of the representative autoantibodies detectable in patients with systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD). Generally, posttranslational modifications (PTMs) on autoantigens are proposed to be involved in the production of autoantibodies. In this study, we tried to detect the alteration in PTMs on a U1 small nuclear RNP 68k subunit (U1-68k), a major antigen of anti-RNP antibodies. Peripheral blood mononuclear cells (PBMCs) were obtained from patients with MCTD, SLE, and rheumatoid arthritis (RA), and from healthy donors. U1-68ks in the PBMCs were detected by 2D Western blot (WB), where extracted nuclear proteins were separated by 2DE, followed by the detection of U1-68k using WB. More than 20 PTM isoforms were detected with different molecular weights of 65.0 , 66.5, and 68.0kDa, and different pIs between 6.0 and 8.5. Importantly, the relative intensity of the spot with 66.5 kDa and pI 7.5 was significantly increased in the MCTD and SLE groups compared to the RA and healthy groups. Further, this U1-68k isoform, in particular, in its RS domain, was found to have significantly decreased phosphorylation compared to the other isoforms. The PTM alternation may be one of the steps to generate the anti-RNP antibodies.     

Adaptive regularizations in an iterative regularized pseudoinverse method

Adaptive regularizations in the implementation of the iterative regularized pseudoinverse method are described. Three different ways of increasing the regularizing parameter are investigated through computer simulations. It is shown that the optimum type of adaptive regularization is identical with the one we have proposed in the previous works.     

Theoretical Study on Intra-Cavity Distributed-Bragg-Reflection Quasi-Phase-Matched Second-Harmonic Lasers

The characteristics of intra-cavity distributed Bragg reflector (DBR) quasi-phase-matched (IDQPM) second-harmonic-generation (SHG) lasers are theoretically studied. In the IDQPM-SHG laser, a QPM device and a DBR for feedback are separately fabricated on the same substrate with the QPM device placed between the DBR and a semiconductor laser. The threshold current of the IDQPM-SHG laser depends on the coupling efficiency between the laser diode and the QPM waveguide and the reflectivity of the DBR. The SH output of the IDQPM-SHG laser is strongly dependent on the generalized SHG conversion efficiency, x. This laser has the potential to attain an SH output over a 30-mW using a currently available 50-mW semiconductor laser for the fundamental light source, when highly efficient QPM device (x=2.2 W⁻¹) is used. Its tolerance for various deviations from the initial design and the problems to develop a commercially available IDQPM-SHG laser are also discussed.