Fluorescence Lymph Node Mapping in Living Mice Using Quantum Dots and a Compression Technique

The lymphatic system is essential in oncology and immunology, and in vivo fluorescence imaging plays a major role in assessing the lymphatic drainage. We investigated non–invasive fluorescence lymph node mapping in mice with special reference to the assessment of deep abdominal lymph nodes. Quantum dots were injected subcutaneously into the rear footpads of mice, and the time course of the fluorescent signal was assessed. Visualization of abdominal lymph nodes was compared with and without compression of the abdomen with transparent, colorless tape at injection doses of 1, 5, and 20 pmol. Popliteal, sacral, iliac, and renal lymph nodes were delineated by non–invasive imaging. Lymph node signals increased up to 3 h after injection. Compression of the abdomen markedly improved the visualization of the iliac nodes, which were invisible at 5 pmol without compression and visible at 1 pmol with compression. Fluorescence lymph node mapping using quantum dots allowed the visualization of deep abdominal lymph nodes in addition to superficial nodes in intact mice, with the aid of a simple compression technique.     

Magnetism of nanographene network influenced by the interaction with acid species

The magnetism of nanographite (stacked nanographene sheets)-based nanoporous carbon is investigated in relation to the interaction with acid guest species. The concentration of the localized spins of non-bonding π-electron state (edge state) localized in the nanographene edges decreases upon the sulfonation of nanographene edges through charge-transfer interaction with sulfonic groups. The sulfonation of nanographene edges enhances the hydrophilic nature of the edges, resulting in the easiness in the water adsorption into the nanopores. This enhances the mechanical compression effect of water molecules condensed in the nanopores on the nanographite domains, resulting in the decrease in the spin concentration. The change in the magnetism upon water uptake reveals ferrimagnetic nature of individual nanographene sheets. The adsorption of HCl having no oxidation ability shows a mechanical effect on the edge-state spins similar to water adsorption. The spin concentration is reduced in two-step manner by the charge-transfer interaction with guest concentrated HNO₃ that is strong oxidant. In the presence of H₂O molecules in diluted HNO₃ the cooperation of mechanical and charge-transfer interactions creates also a two-step change in the magnetism.     

Controllable photoinduced optical attenuation in a single-mode optical fiber by irradiation of a femtosecond pulse laser

Novel optical attenuation fibers were fabricated by the irradiation of a focused infrared femtosecond pulsed laser onto the core of a silica glass single-mode optical fiber. Optical attenuation at a wavelength of 1.55 microm proportionally increased with increasing numbers of irradiation points and was controllable under laser irradiation conditions. The single-mode property of the waveguide and the mode-field diameter of the optical fiber were maintained after irradiation of the femtosecond laser. It is suggested that the attenuation results from optical scattering at photoinduced spots formed inside the fiber core.     

Z(2) gauge neural network and its phase structure

We study general phase structures of neural-network models that have Z(2) local gauge symmetry. The Z(2) spin variable _Si=±1$S_i=\pm 1$ on the i$i$-th site describes a neuron state as in the Hopfield model, and the Z(2) gauge variable _Jij=±1$J_{ij}=\pm 1$ describes a state of the synaptic connection between j$j$-th and i$i$-th neurons. The gauge symmetry allows for a self-coupling energy among _Jij$J_{ij}$’s such as _JijJjkJki$J_{ij}{J}_{jk}{J}_{ki}$, which describes reverberation of signals. Explicitly, we consider the three models; (I) an annealed model with full and partial connections of _Jij$J_{ij}$, (II) a quenched model with full connections where _Jij$J_{ij}$ is treated as a slow quenched variable, and (III) a quenched three-dimensional lattice model with the nearest-neighbor connections. By numerical simulations, we examine their phase structures paying attention to the effect of the reverberation term, and compare them with each other and with the annealed 3D lattice model which has been studied beforehand. By noting the dependence of thermodynamic quantities upon the total number of sites and the connectivity among sites, we obtain a coherent interpretation to understand these results. Among other things, we find that the Higgs phase of the annealed model is separated into two stable spin-glass phases in the quenched models (II) and (III).     

Combinatorial and approximative analyses in a spatially random division process

For a spatial characteristic, there exist commonly fat-tail frequency distributions of fragment-size and -mass of glass, areas enclosed by city roads, and pore size/volume in random packings. In order to give a new analytical approach for the distributions, we consider a simple model which constructs a fractal-like hierarchical network based on random divisions of rectangles. The stochastic process makes a Markov chain and corresponds to directional random walks with splitting into four particles. We derive a combinatorial analytical form and its continuous approximation for the distribution of rectangle areas, and numerically show a good fitting with the actual distribution in the averaging behavior of the divisions.     

A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric observations and its implications to the volcanic activity

Taal Volcano is one of the most active volcanoes in the Philippines. The magnetotelluric 3D forward analyses indicate the existence of a large high resistivity anomaly (∼100 Ω·m) with a volume of at least 3 km × 3 km × 3 km, which is capped by a conductive layer (∼10 Ω·m), beneath the Main Crater. This high resistivity anomaly is hypothesized to be a large hydrothermal reservoir, consisting of the aggregate of interconnected cracks in rigid and dense host rocks, which are filled with hydrothermal fluids coming from a magma batch below the reservoir. The hydrothermal fluids are considered partly in gas phase and liquid phase. The presence of such a large hydrothermal reservoir and the stagnant magma below may have influences on the volcano’s activity. Two possibilities are presented. First, the 30 January 1911 explosion event was a magmatic hydrothermal eruption rather than a base-surge associated with a phreato-magmatic eruption. Second, the earlier proposed four eruption series may be better interpreted by two cycles, each consisting of series of summit and flank eruptions.     

Magnesium K‐edge XANES spectroscopy of geological standards

Magnesium K‐edge X‐ray absorption near‐edge structure (XANES) spectra have been investigated to develop a systematic understanding of a suite of Mg‐bearing geological materials such as silicate and carbonate minerals, sediments, rocks and chemical reagents. For the model compounds the Mg XANES was found to vary widely between compounds and to provide a fingerprint for the form of Mg involved in geologic materials. The energy positions and resonance features obtained from these spectra can be used to specify the dominant molecular host site of Mg, thus shedding light on Mg partitioning and isotope fractionation in geologic materials and providing a valuable complement to existing knowledge of Mg geochemistry.     

Molecular dynamics simulations of structural disordering and forming defects in a milling process for selenium

In our previous paper, structural changes of selenium powders ground by a planetary ball mill at various rotational speeds were investigated for the nanostructural modification of particles using mechanical grinding process. The experimental results indicated that the amorphisation of Se by grinding accompanies lattice strain, and the lattice strain arises from impact energy which is more than an energy related to intermolecular interaction. In this paper, molecular dynamics simulations of selenium have been carried out under compressing conditions of various pressure strengths for obtaining information of the lattice strain at atomic level. Then, dynamical behaviour of atomic configuration has been discussed in this process. The structural disordering and formation of the structural defects were estimated by deviations of bond length and angle and the number of created defects before and after compressing from simulated results. The disordering took place during compressing at various pressure strengths, and the disordered atoms return to their initial positions at lower pressure. Stable disordered state and defects after the compression can however remain by compression at more than a certain pressure strength mainly associated with binding energy of selenium.     

Magnetic structures of exchange bias Ni/FeF2(1 1 0) interface

Electronic and magnetic structures of ferromagnetic (FM)/antiferromagnetic (AFM), Ni/FeF₂(1 1 0), with a compensated AFM interface are investigated by using the full-potential linearized augmented plane-wave method. We find that magnetic structures at the AFM interface are perturbed by a contact with the FM material, where the superexchange interaction through the interface F excites and induces a small net moment at the AFM interface. These results predicted may play an important role for explaining the exchange bias in this system, and rule out the exchange bias mechanisms with the spin-flop coupling and the magnetic moment reorientation.