Direct observation of surfactant aggregate behavior on a mica surface using high-speed atomic force microscopy

The processes of dynamic aggregate transformations of micelles at a mica surface were observed using high-speed atomic force microscopy. We showed that salt concentration affects not only the equilibrium state adsorbed structure but also the time required to reach the equilibrium state on the mica surface.     

Selective labeling of the endoplasmic reticulum in live cells with silicon quantum dots

A simple and novel approach was developed to obtain water-dispersible silicon quantum dots (Si-QDs) of low toxicity that were able to selectively label the endoplasmic reticulum (ER) in live cells. A block copolymer (Pluronic F127) was used to coat the surface of Si-QDs. Si-QDs form aggregates with diameters of 20-40 nm and show an outstanding optical stability upon UV irradiation. Our F127-treated Si-QDs would be a powerful tool for long-term real-time observation of the ER in live cells.     

A combined quantum mechanical and molecular mechanical method using modified generalized hybrid orbitals: implementation for electronic excited states

The generalized hybrid orbital (GHO) method is implemented at the second-order approximate coupled cluster singles and doubles (CC2) level for quantum mechanical (QM)/molecular mechanical (MM) electronic excited state calculations. The linear response function of CC2 in the GHO scheme is derived and implemented. The new implementation is applied to the first singlet excited states of three aromatic amino acids, phenylalanine, tyrosine, and tryptophan, and also bacteriorhodopsin for assessment. The results obtained for aromatic amino acids agreed well with the full QM CC2 calculations, while the calculated excitation energies of bacteriorhodopsin and its chromophore, all-trans retinal, reproduced the environmental shift of the experimental data. For the bacteriorhodopsin case, the environmental shift of GHO also showed good agreements with the experimental data. The contribution of the quantum effect of certain moieties in the excited states is elucidated by changing the partitioning of QM and MM regions.     

Fast on-demand droplet fusion using transient cavitation bubbles

A method for on-demand droplet fusion in a microfluidic channel is presented using the flow created from a single explosively expanding cavitation bubble. We test the technique for water-in-oil droplets, which are produced using a T-junction design in a microfluidic chip. The cavitation bubble is created with a pulsed laser beam focused into one droplet. High-speed photography of the dynamics reveals that the droplet fusion can be induced within a few tens of microseconds and is caused by the rapid thinning of the continuous phase film separating the droplets. The cavitation bubble collapses and re-condenses into the droplet. Droplet fusion is demonstrated for static and moving droplets, and for droplets of equal and unequal sizes. Furthermore, we reveal the diffusion dominated mixing flow and the transport of a single encapsulated cell into a fused droplet. This laser-based droplet fusion technique may find applications in micro-droplet based chemical synthesis and bioassays.     

Imaging of EdU, an alkyne-tagged cell proliferation probe, by Raman microscopy

Click-free imaging of the nuclear localization of an alkyne-tagged cell proliferation probe, EdU, in living cells was achieved for the first time by means of Raman microscopy. The alkyne tag shows an intense Raman band in a cellular Raman-silent region that is free of interference from endogenous molecules. This approach may eliminate the need for click reactions in the detection of alkyne-labeled molecules.     

Preparation and evaluation of orally rapidly disintegrating tablets containing taste-masked particles using one-step dry-coated tablets technology

In this study, in order to address the problems with manufacturing orally rapidly disintegrating tablets (ODT) containing functional (taste masking or controlled release) coated particles, such as the low compactability of coated particles and the rupture of coated membrane during compression, a novel ODT containing taste-masked coated particles (TMP) in the center of the tablets were prepared using one-step dry-coated tablets (OSDrC) technology. As a reference, physical-mixture tablets (PM) were prepared by a conventional tableting method, and the properties of the tablets and the effect of compression on the characteristics of TMP were evaluated. OSDrC was found to have higher tensile strength and far lower friability than PM, but the oral disintegration time of OSDrC is slightly longer than that of PM following high compression pressure. Consequently, OSDrC approaches the target tablet properties of ODT, whereas PM does not. The deformation of TMP in OSDrC due to compression is slight, and the release rate of acetaminophen (AAP) from OSDrC is the same as from TMP. However, TMP on the surface of PM are considerably deformed, and the release rate of AAP from PM is faster than from TMP. These findings suggest that OSDrC technology is a useful approach for preparing ODT containing functional coated particles. Furthermore, we demonstrate that the elastic recovery of tablets can affect differences in the properties of OSDrC, PM and placebo tablets (PC).     

Nonlinear normal modes and primary resonance of horizontally supported Jeffcott rotor

The nonlinear normal modes of a horizontally supported Jeffcott rotor are investigated. In contrast with a vertically supported rotor, there are localized and nonlocalized nonlinear normal modes because the linear natural frequencies in the horizontal and vertical directions are slightly different due to both gravity and the nonlinearity of restoring force. Reflecting such nonlinear normal modes, the frequency response curves are characterized in the primary resonance. In the case where the eccentricity is small, i.e., the response amplitude is small, the whirling motion is localized in the horizontal or vertical direction in the resonance. On the other hand, when the eccentricity is large, two kinds of whirling motion, which are localized in the vertical direction and nonlocalized in any direction, coexist simultaneously in a region of rotational speed. Experiments are conducted, and the theoretically predicted nonlinear responses based on localized and nonlocalized nonlinear normal modes are observed.