Nanometer-sized gelatin particles prepared by means of gamma-ray irradiation

Nanometer-sized gelatin particles have been prepared by means of gamma-ray irradiation and characterized by static and dynamic light scattering combined with circular dichroism (CD) measurements. The molecular weight of the nanoparticles was much larger than that of the original gelatin molecules, whereas the hydrodynamic radius was much smaller. Radius of gyration evaluated from the angular dependence of the static light scattering intensity decreased with increasing irradiation dose. CD spectra of the gelatin nanoparticles were independent of temperature, and it is suggested that the nanoparticles consist of highly and randomly packed gelatin and their conformation is stable against the temperature change.     

Effect of kappa-carrageenan on the properties of poly(N-vinyl pyrrolidone)/kappa-carrageenan blend hydrogel synthesized by γ-radiation technology

A series of hydrogels in the form of rods were prepared from kappa-carrageenan (KC) and poly (N-vinyl pyrrolidone) (PVP) by gamma radiation with ⁶⁰Co γ source at room temperature. The properties of the prepared hydrogels, such as the gel strength, gel fraction and swelling behavior were investigated. Incorporation of KC into the PVP/water system increased obviously the gel strength and equilibrium degree of swelling (EDS) of PVP hydrogel. The experimental analyses showed that the crosslinking reaction of PVP was quicker than the degradation of KC at a low dose (less than 30 kGy), and the degradation of KC was inhibited in the PVP/KC mixture system. So an interpenetrating polymer network (IPN) hydrogel composed of PVP (a chemical crosslinking network) and KC (a physical crosslinking network) was proposed here. The existence of different classes of water in this IPN system was shown by water melting curves using DCS.     

Sub‐Bandgap Excitation‐Induced Electron Injection from CdSe Quantum Dots to TiO2 in a Directly Coupled System

We show that the sub‐bandgap excitation of a directly coupled CdSe quantum dot (QD)–TiO₂ system induces electron injection from CdSe levels to the conduction band of TiO₂, leading to spectral extension of the light response. We anticipate that this study presents a useful guideline for improving the conversion efficiency of QD‐sensitized solar cells.     

Inclusion and Release of Hinokitiol into/from MCT-β-CD Fixed on Japanese Washi Paper

The potential for surface modification of paper by modified cyclodextrins was demonstrated by the model system of Japanese washi paper and monochlorotriazinyl-β-cyclodextrin (MCT-β-CD). MCT-β-CD was covalently bonded to the paper. The optimal bonded reaction conditions were found to be 10 min at 150 °C with a moisture content of less than 2.5 (g water/g dry paper). The bounded MCT-β-CD on the paper was able to include and release hinokitiol representing the group of antibacterial agents. The maximum molar inclusion ratio of hinokitiol in the immobilized MCT-β-CD was around 0.8. The release rates of hinokitiol, included in the fixed MCT-β-CD, were monitored at 50 °C for different relative humidities. The release rate was strongly influenced by the relative humidity. These results demonstrate that the antibacterial agent can be included and released from MCT-β-CD fixed on the paper. The antibacterial activity of the fixed hinokitiol against airborne microorganisms was demonstrated.     

Experimental verification of laser photocathode RF gun as aninjector for a laser plasma accelerator

The feasibility of the laser photocathode RF gun, BNL/GUN-IV, as an injector for a laser plasma accelerator was investigated at the subpicosecond S-band twin linac system of the Nuclear Engineering Research Laboratory, University of Tokyo. Electron beam energy of 16 MeV, emittance of 6π mm mrad, bunch length of 240 fs (FWHM), and charge per bunch of 350 pC were confirmed at 10 Hz. As for diagnosis of the femtosecond electron bunch, the quantitative comparison of performance of the femtosecond streak camera, the coherent transition radiation (CTR) Michelson interferometer, and the far-infrared polychromator was carried out. We concluded that the streak camera is the most reliable up to 200 fs and that the polychromator is the best for the shorter electron bunch. The 3.5-ps (rms) resolved synchronization between the YLF laser driver for the gun and the electron bunch was achieved. Based on the above experiences, we have designed and installed a much better laser-electron synchronization system using the Kerr-lens mode-locked Ti:Sapphire laser with the min harmonics synchrolocker and the stable 15-MW klystron. The timing jitter is expected to be suppressed down to 320 fs (rms)     

Prediction of the layered ink layout for 3D printers considering a desired skin color and line spread function

Optical Review - We propose a layout estimation method for multi-layered ink using a measurement of the line spread function (LSF) and machine learning. The three-dimensional printing market for...     

Highly Emissive Boron Ketoiminate Derivatives as a New Class of Aggregation‐Induced Emission Fluorophores

A series of boron ketoiminate derivatives that exhibited clear aggregation‐induced emission (AIE) characteristics (in THF: Φ_PL≤0.01; in the solid state: Φ_PL=0.30–0.76) were prepared by the reactions of 1,3‐enaminoketone derivatives with boron trifluoride–diethyl etherate. The structures and optical properties were investigated by UV‐visible spectroscopy, photoluminescent (PL) spectroscopy, and X‐ray single‐crystal measurements. These results indicate that the AIE characteristics were derived from molecular motions of the boron‐chelating rings with a boron? nitrogen (B? N) bond. Furthermore, the optical properties were controllable by steric hindrance of the substituted groups on the nitrogen atom.     

Two‐Photon‐Responsive Supramolecular Hydrogel for Controlling Materials Motion in Micrometer Space

Spatiotemporal control of fluidity inside a soft matrix by external stimuli allows real‐time manipulation of nano/micromaterials. In this study, we report a two‐photon‐responsive peptide‐based supramolecular hydrogel, the fluidity of which was dramatically controlled with high spatial resolution (10 μm×10 μm×10 μm). The off–on switching of the Brownian motion of nanobeads and chemotaxis of bacteria by two‐photon excitation was successfully demonstrated.     

Aging properties of radiation vulcanized NR latex film

A simple method was developed to evaluate the antioxidant activity for radiation vulcanized natural rubber latex. Tris(nonylated phenyl) phosphite has been selected as the effective antioxidant. This antioxidant is prone to hydrolyze under high humidity condition, resulting in the easy decomposition of radiation vulcanizate in the environment.