Femtosecond laser-induced crystallization of protein in gel medium

We succeeded in generating femtosecond laser-induced crystallization of hen egg-white lysozyme (HEWL) in the irradiated area by suppressing convection of the solution using a highly concentrated gel. When a laser pulse, whose energy was above the threshold energy for bubble formation, was focused along with a linear scanning of the stage, HEWL crystallization was enhanced at the surface of bubbles on the irradiated line. The relation between the bubble formation process and the crystallization is discussed.     

Nondestructive isolation of single cultured animal cells by femtosecond laser-induced shockwave

A shockwave induced by focusing an intense femtosecond laser onto a culture medium under a microscope was used to manipulate single cultured animal cells. Mouse NIH3T3 fibroblasts were cultured on a collagen matrix and placed on a microscope installation that included an intense femtosecond laser. Cells were detached individually from the matrix by the shockwave, after their filopodia were cut by focusing the laser directly on them. The appearance and locomotion of cells after detachment was monitored with a CCD camera. Filopodia of the detached cells were regenerated, and the cell adhered again to the matrix within 4 hrs after detachment. When the shockwave was induced at a pulse energy of 0.72 J/pulse, 80% of cells were successfully detached from the culture plate in a non-destructive manner. The force required to detach a cell was estimated to be a few N/m², which is larger than the photon force resulting from conventional laser trapping. PACS 42.62.Be; 47.40.Nm; 87.80.Rb     

Direct measurement of the energy gap of superfluid 3He-B in the low-temperature limit

The zero-temperature limit of the energy gap, Delta(P,T-->0), of superfluid 3He-B has been measured at T/T(c) less, similar0.25, near 0.1 and 4.8 bars, and in zero magnetic field. The energy gap was determined from the 2Delta pair-breaking edge of an acoustic signal obtained by novel, pulsed Fourier-Transform ultrasonic spectroscopy. Our results are independent of the temperature scale and the theoretical model of the gap. The values for Delta(P,T-->0) are lower than predicted by the weak-coupling-plus theory, and the Delta(P approximately 0.1 bars,T-->0) values are lower than predicted by BCS theory. The data indicate that Delta(P,T-->0) of superfluid 3He-B is not well modeled at the lowest pressures.     

Ultrasound attenuation of superfluid 3He in aerogel

We have performed longitudinal ultrasound (9.5 MHz) attenuation measurements in the B phase of superfluid 3He in 98% porosity aerogel down to the zero temperature limit for a wide range of pressures at zero magnetic field. The absolute attenuation was determined by direct transmission of sound pulses. Compared to the bulk fluid, our results revealed a drastically different behavior in attenuation, which is consistent with theoretical accounts with gapless excitations and a collision drag effect.     

Impact of disorder on the 5/2 fractional quantum Hall state

We compare the energy gap of the ν = 5/2 fractional quantum Hall effect state obtained in conventional high mobility modulation-doped quantum-well samples with those obtained in high quality GaAs transistors (heterojunction insulated gate field-effect transistors). We are able to identify the different roles that long-range and short-range disorders play in the 5/2 state and observe that the long-range potential fluctuations are more detrimental to the strength of the 5/2 state than short-range potential disorder.     

Spatiotemporal Dynamics of Aggregation‐Induced Emission Enhancement Controlled by Optical Manipulation

We present spatiotemporal control of aggregation‐induced emission enhancement (AIEE) of a protonated tetraphenylethene derivative by optical manipulation. A single submicrometer‐sized aggregate is initially confined by laser irradiation when its fluorescence is hardly detectable. The continuous irradiation of the formed aggregate leads to sudden and rapid growth, resulting in bright yellow fluorescence emission. The fluorescence intensity at the peak wavelength of 540 nm is tremendously enhanced with growth, meaning that AIEE is activated by optical manipulation. Amazingly, the switching on/off of the activation of AIEE is arbitrarily controlled by alternating the laser power. This result means that optical manipulation increases the local concentration, which overcomes the electrostatic repulsion between the protonated molecules, namely, optical manipulation changes the aggregate structure. The dynamics and mechanism in AIEE controlled by optical manipulation will be discussed from the viewpoint of molecular conformation and association depending on the laser power.