Role of mixing thermodynamic properties on the Soret effect.

We demonstrate that the modified Kempers model, a recently developed theoretical model for the Soret effect in oxide melts, is applicable for predicting the composition dependence of the Soret coefficient in three binary molecular liquids with negative enthalpies of mixing. We compared the theoretical and experimental values for water/ethanol, water/methanol, water/ethylene glycol, water/acetone, and benzene/n-heptane mixtures. In water/ethanol, water/methanol, and water/ethylene glycol, which have negative enthalpies of mixing across the entire mole fraction range, the modified Kempers model successfully predicts the sign change of the Soret coefficient with high accuracy, whereas, in water/acetone and benzene/n-heptane, which have composition ranges with positive enthalpies of mixing, it cannot predict the sign change of the Soret coefficient. These results suggest that the model is applicable in composition ranges with negative enthalpies of mixing and provides a framework for predicting and understanding the Soret effect from the equilibrium thermodynamic properties of mixing, such as the partial molar volume, partial molar enthalpy of mixing, and chemical potential.

Determination of thermodynamic and microscopic origins of the Soret effect in sodium silicate melts: Prediction of sign change of the Soret coefficient.

The Soret effect in silicate melts has attracted attention in earth and material sciences, particularly in glass science and engineering, because a compositional change caused by the Soret effect modifies the material properties of silicate melts. We investigated the Soret effect in an Na2O-SiO2 system, which is the most common representative of silicate melts. Our theoretical approach based on the modified Kempers model and non-equilibrium molecular dynamics simulation was validated for 30Na2O-70SiO2(mol. %). The sign and order of the absolute values of the calculated Soret coefficients were consistent with the experimental values. The positive Soret coefficient of SiO2 in the SiO2-poor composition range was accurately predicted. Previous experimental studies have focused on SiO2-rich compositions, and only the negative sign, indicating SiO2 migration to the hot side, has been observed. In the SiO2-poor composition range, the Q0 structure was dominant and had four Si-O-Na bonds around an SiO4 unit. The Si-O-Na bond had high enthalpic stability and contributed to the large negative enthalpy of SiO2 mixing. According to our model, components with a large negative partial molar enthalpy of mixing will concentrate in the cold region. The microscopic and thermodynamic origins of the sign change in the Soret effect were determined.

Role of partial molar enthalpy of oxides on Soret effect in high-temperature CaO-SiO2 melts.

The Soret effect or thermodiffusion is the temperature-gradient driven diffusion in a multicomponent system. Two important conclusions have been obtained for the Soret effect in multicomponent silicate melts: first, the SiO2 component concentrates in the hot region; and second, heavier isotopes concentrate in the cold region more than lighter isotopes. For the second point, the isotope fractionation can be explained by the classical mechanical collisions between pairs of particles. However, as for the first point, no physical model has been reported to answer why the SiO2 component concentrates in the hot region. We try to address this issue by simulating the composition dependence of the Soret effect in CaO-SiO2 melts with nonequilibrium molecular dynamics and determining through a comparison of the results with those calculated from the Kempers model that partial molar enthalpy is one of the dominant factors in this phenomenon.

The pyrite-type high-pressure form of FeOOH.

Water transported into Earth's interior by subduction strongly influences dynamics such as volcanism and plate tectonics. Several recent studies have reported hydrous minerals to be stable at pressure and temperature conditions representative of Earth's deep interior, implying that surface water may be transported as far as the core-mantle boundary. However, the hydrous mineral goethite, α-FeOOH, was recently reported to decompose under the conditions of the middle region of the lower mantle to form FeO2 and release H2, suggesting the upward migration of hydrogen and large fluctuations in the oxygen distribution within the Earth system. Here we report the stability of FeOOH phases at the pressure and temperature conditions of the deep lower mantle, based on first-principles calculations and in situ X-ray diffraction experiments. In contrast to previous work suggesting the dehydrogenation of FeOOH into FeO2 in the middle of the lower mantle, we report the formation of a new FeOOH phase with the pyrite-type framework of FeO6 octahedra, which is much denser than the surrounding mantle and is stable at the conditions of the base of the mantle. Pyrite-type FeOOH may stabilize as a solid solution with other hydrous minerals in deeply subducted slabs, and could form in subducted banded iron formations. Deep-seated pyrite-type FeOOH eventually dissociates into Fe2O3 and releases H2O when subducted slabs are heated at the base of the mantle. This process may cause the incorporation of hydrogen into the outer core by the formation of iron hydride, FeHx, in the reducing environment of the core-mantle boundary.

Localized control of light-matter interactions by using nanoscale asymmetric TiO2.

This paper reports an asymmetry structure-mediated route for highly localized control of light-matter interactions by using tapered TiO(2). We demonstrate for the first time that the growth habit of Ag nanostructures on tapered TiO(2) can be tuned by controllable photolysis. Site-selective anchoring of Ag nanoparticles or nanowires on tapered TiO(2) can be achieved by simply changing the external light. We further show that the obtained tapered TiO(2)-Ag hetero-nanostructures present excellent light-trapping ability over a wide range of wavelengths which is considered to originate from the unique synergistic effects of graded waveguiding and plasmonic light trapping. This improved photon-management capability renders the prepared substrate a very promising candidate for optical sensing application. For this purpose, an enhanced sensitivity for trace detection is confirmed. These findings open up promising avenues for tailoring of light-matter interactions which are of special interest for studying controllable photolysis activation processes and diverse applications such as nanostructure growth, trace detection, photocatalysis and solar cells.

A Photoconductive, Thiophene-Fullerene Double-Cable Polymer, Nanorod Device.

Gold/double-cable copolymer/gold multisegmented nanorods were prepared electrochemically via a template-based method. These "bulk heterojunction" nanorods showed photoconductivity providing us with a platform to study photoinduced charge separation/transport at the nanointerface and begin to think about the rational design of nanoscale solar cells based on such structures.

Observation of laser-induced stress waves and mechanism of structural changes inside rock-salt crystals.

The structural changes inside rock-salt crystals after femtosecond (fs) laser irradiation are investigated using a microscopic pump-probe technique and an elastic simulation. The pump-probe imaging shows that a squircle-shaped stress wave is generated after the fs laser irradiation as a result of the relaxation of thermal stress in the photoexcited region. Pump-probe crossed-Nicols imaging and elastic simulation elucidate that shear stresses and tensile stresses are concentrated in specific regions during the propagation of the stress wave. The shear stresses and tensile stresses observed in this study can explain the characteristic laser-induced structural changes inside rock-salt crystals.

Formation mechanism of element distribution in glass under femtosecond laser irradiation.

We report on the formation mechanism of element distribution in glass under high-repetition-rate femtosecond laser irradiation. We simultaneously focused two beams of femtosecond laser pulses inside a glass and confirmed the formation of characteristically shaped element distributions. The results of the numerical simulation in which we considered concentration- and temperature-gradient-driven diffusions were in excellent qualitative agreement with the experimental results, indicating that the main driving force is the sharp temperature gradient. Since the composition of a glass affects its refractive index, absorption, and luminescence property, the results in this study provide a framework to fabricate a functional optical device such as optical circuits with a high-repetition-rate femtosecond laser.

Intermetallic magnetic nanoparticle precipitation by femtosecond laser fragmentation in liquid.

Intermetallic Nd(2)Fe(14)B nanoparticles with an average diameter of 30 nm, which are smaller than a theoretical single magnetic domain size of 220 nm, were successfully prepared by the femtosecond laser fragmentation in liquid. The self-passivating amorphous carbon layer resulting from the decomposition of the surrounding solvent prevents the Nd(2)Fe(14)B nanoparticle from aggregation and oxidation. The coercivity of Nd(2)Fe(14)B nanoparticle increases with increase of the laser irradiation time, despite the reduction of crystallinity.

Simultaneous tailoring of phase evolution and dopant distribution in the glassy phase for controllable luminescence.

Construction of an active composite with multicolor visible and broadband near-infrared luminescence is of great technological importance for various applications, including three-dimensional (3D) display, broadband telecommunication, and tunable lasers. The major challenge is the effective management of energy transfer between different dopants in composite. Here we present an in situ strategy for controlling energy transfer between multiple active centers via simultaneous tailoring of the evolution of phases and the distribution of dopants in the glassy phase. We show that the orderly precipitation of Ga(2)O(3) and LaF(3) nanocrystals and the selective incorporation of Ni(2+) and Er(3+) into them can be achieved. The obtained composite shows unique multicolor visible and broadband near-infrared emission. Possible mechanisms for the selective doping phenomenon are proposed, based on thorough structural and optical characterizations and crystal-field calculation results. Moreover, the strategy can be successfully extended to accomplish space-selective control of multicolor luminescence by employing the modulated stimulation field. The results suggest that the strategy could be applied to fabricate a multifunctional light source with a broad range of important host/activator combinations and to construct various types of three-dimensional active microstructures.

Good solvent effects of C70 cluster formations and their electron-transporting and photoelectrochemical properties.

Good solvent effects of C(70) cluster formations and their electron-transporting and photoelectrochemical properties have been systematically examined for the first time. Nano-to-micrometer scale assemblies of C(70) with different morphologies were prepared by rapidly injecting poor solvent (i.e., acetonitrile) into a solution of C(70) dissolved in various good solvents (i.e., benzene, toluene, chlorobenzene, etc). The cluster morphology engineering was successfully achieved by changing the good solvent, yielding the spherical, rodlike, or platelike clusters in the mixed solvents. The clusters of C(70) were electrophoretically deposited onto a nanostructured SnO(2) electrode to examine the photoelectrochemical properties under the white light or monochromatic light illumination. The maximum incident photon-to-current efficiency (IPCE) varied from 0.8 to 10% depending on the combinations of the poor-good solvents. The differences in the IPCE values are discussed in terms of the surface area, thickness, and electron mobility of the deposited cluster films. The electron mobility is found to be the most predominant factor for the IPCE, indicating the importance of the electron-transporting process in the overall photocurrent generation. In addition, the electron mobility is closely correlated with the underlying molecular alignment and the resultant cluster structure. Thus, these results will provide basic clue for the design of C(70)-based molecular devices including the organic photovoltaics.

Ultrashort pulse manipulation of ZnO nanowire growth.

A procedure of femtosecond pulse laser irradiation was incorporated into the synthesis of zinc oxide (ZnO) nanowires in aqueous solutions to investigate the photo-initiated heterogeneous nucleation induced by the irradiation and the associated nanowire growth. Elongated ZnO nanowires with smooth planes and end tips were successfully grown following the irradiation process and subsequent hydrothermal treatments in a catalyst-free environment, compared to aggregated flower-like nanostructures with porous and rough surfaces, grown from homogeneous nucleation without laser irradiation. Studies using femtosecond laser systems at 1 kHz and 250 kHz repetition rates show that the pulse energy is critical in the heterogeneous nucleation process for the growth of ZnO nanowires. A minimum threshold pulse energy, 200 microJ/pulse for the 1 kHz system and 2.4 microJ/pulse for 250 kHz, is observed beyond which well-defined and individually separated nanowires were grown. Thermal effect caused by the 250 kHz repetition rate provides a counter-balance to the low pulse energy required for the growth process. XRD analysis of the nanowires reveals a hexagonal structure while photoluminescence shows emission at about 385 nm. The overall results show that the pulse energy is critical for heterogeneous nucleation while the irradiation duration affects the density of nucleation, which together with the hydrothermal treatment temperature influence the growth rate and thus the morphology of the nanowires.

Extramammary Paget's disease/carcinoma successfully treated with a combination chemotherapy: report of two cases.

We have treated two patients with extramammary Paget's disease/carcinoma (EMPD/C), a 62-year-old woman and a 78-year-old man. In both patients, lymph nodes in the areas of the bilateral inguinal, external iliac arteries, and abdominal aorta were affected. After surgery, they underwent 5 courses of systemic combination chemotherapy at 4-week intervals to residual or recurrent lymph node metastasis. Each course consisted of 3.5 mg mitomycin C and 50 mg epirubicin (day 1), 0.6 mg vincristine (days 1 and 7), 30 mg cisplatin (days 1, 2, and 3), and 350 mg 5-fluorouracil (days 3, 4, 5, 6, and 7). The affected lymph nodes in both patients subsided in response to the chemotherapy. Positron emission tomography (PET) scans confirmed the complete remission of lymph node metastasis in Case 1. In Case 2, they were reduced by more than 90% on computed tomography (CT) scans. Adverse effects included leukocytopenia, vomiting, hypesthesia, and constipation, all of which disappeared after the completion of chemotherapy. While surgery with wide local excision is the treatment of choice in patients with EMPD/C, there is currently no standardized treatment for advanced cases with metastasis. We describe two patients with EMPD/C whose metastatic lesions responded well to this combination of chemotherapy.

Estrogen dermatitis: a dendritic-cell-mediated allergic condition.

BACKGROUND: Most estrogen dermatitides are induced by local or systemic contact dermatitis where dendritic cells are central, and tamoxifen has a blocking effect on dendritic cells. METHODS: We present 5 cases of estrogen dermatitis in which the clinical features were prurigo, urticaria, acneiform eruption and annular erythema. RESULTS: Tamoxifen was effective in 3 of 4 cases. Three of 4 biopsy specimens showed the formation of Langerhans cell nests in the epidermis and hair follicles and perivascular infiltration of CD4+ and CD8+ lymphocytes in the dermis. CONCLUSION: These results suggest that a dendritic-cell-mediated allergic mechanism is involved in estrogen dermatitis.