Passive dual-probe near-field microscopy.

Accurate and simultaneous multiposition near-field measurements are essential to study the time-dependent local dynamics, including heat and carrier transfer. The existing passive long-wavelength infrared (LWIR) scattering-type scanning near-field optical microscopy (s-SNOM) systems with a single probe cannot perform precise near-field measurements of the heat or carrier transporting process at the nanoscale level. Therefore, in this study, we developed a passive LWIR s-SNOM system with two probes. To test the effectiveness of the proposed passive LWIR dual-probe s-SNOM system, each probe was precisely controlled using a shear-force feedback system, and the mechanical interference between the probes was used to monitor the distance between the probes. We achieved simultaneous near-field measurements at two different positions 500 nm apart using the proposed passive LWIR dual-probe s-SNOM system. The simultaneously detected near-field signals from two different points were extracted individually, making this technique an effective nanoscale analysis tool for local carrier dynamics.

Passive near-field imaging via grating-based spectroscopy.

Passive scattering-type scanning near-field optical microscopy (s-SNOM) has recently been developed for studying long-wavelength infrared (LWIR) waves. It detects surface-localized waves without any external illumination or heating and enables the imaging of hot-electron energy dissipation and nanoscale Joule heating. However, the lack of a wavelength selection mechanism in the passive LWIR s-SNOM makes it difficult to perform a thorough analysis of the surface-localized waves. Here, we develop a novel passive scanning near-field optical spectroscopy with a diffraction grating. The spectroscopic optics are designed to exhibit a high signal efficiency and mechanical performance at the temperature of liquid helium (4.2 K). Using the developed passive LWIR near-field spectroscopy, the spectral information of thermally excited evanescent waves can be directly obtained without any influence from the external environment factors, including environmental heat. We have detected the thermally excited evanescent waves on a SiC/Au micropatterned sample at room temperature with a spatial resolution of 200 nm and a wavelength resolution of 500 nm at several wavelengths in the range of 14-15 µm. The obtained spectra are consistent with the electromagnetic local density of states calculated based on the fluctuation-dissipation theorem. The developed passive LWIR near-field spectroscopy enables the spectral analysis of ultrasmall surface-localized waves, making it a high-performance surface analysis tool.

Low energy excitation in liquid Sb and liquid Bi observed in inelastic x-ray scattering spectra.

The dynamic structure factorS(Q,E), whereQandEare momentum and energy transfer, respectively, has been measured for liquid Sb, using inelastic x-ray scattering. A modified damped harmonic oscillator model function was applied to analyseS(Q,E) of liquid Sb and also to that of liquid Bi by Inuiet al(2015Phys. Rev.B92, 054206). The obtained excitation energy was in fairly good agreement with that predicted byab initiomolecular dynamics simulations on these liquid semi-metals. The excitation energy of the longitudinal acoustic mode in liquid Sb and liquid Bi exhibits flat-toppedQdependence whereas the lower excitation energy below the longitudinal acoustic excitation showsQ-gap behaviour. From the viscosity estimated from theQ-gap experimentally obtained, it is inferred that the lower energy excitation arises from the transverse acoustic excitation in the liquids.

Experimental observation of density fluctuations in liquid metals associated with liquid-liquid, liquid-gas and metal-nonmetal transitions.

We have developed a special technique and succeeded to carry out small-angle x-ray scattering measurements for some liquid metal systems. The purpose is to investigate effects of transitions such as liquid-liquid (LLT), liquid-gas (LGT) and metal-nonmetal (MNMT) transitions on mesoscopic density fluctuations in liquids. In liquid Te systems (Se-Te and Ge-Te mixtures), which show continuous LLT accompanying MNMT, parameters of density fluctuations show maxima almost in the middle of the transition, both in strength and spatial size. This work (and Kajihara et al 2012 Phys. Rev. B86 214202) was the first direct observation that density fluctuations exhibit maximum corresponding to LLT. However in this study, we could not clearly separate the effects of LLT and MNMT on the observed density fluctuations. Thus, we also investigated fluid Hg under high pressure and high temperature conditions, which shows MNMT near a critical point of LGT, to investigate how MNMT affects them. We observed distinct density fluctuations; a strength and a correlation length of them show maxima at around a critical isochore of LGT, and the former is basically consistent with a phase diagram (compressibility) of LGT; they do not show any peaks at MNMT region. Precise analysis revealed that MNMT only affects a shift of another parameter, a short-range correlation length. These results in fluid Hg indicate that the density fluctuations are mainly derived from a critical phenomena of LGT and MNMT does not play any critical role on them. We believe that the latter conclusion also holds true for liquid Te systems; MNMT plays no important role on the density fluctuations in liquid Te systems and LLT is the main origin of them.

Peculiar temperature dependence of dynamical sound speed in liquid Se50Te50 by inelastic x-ray scattering.

Inelastic x-ray scattering (IXS) measurements were carried out on liquid Se50Te50 at temperatures up to 1323 K to investigate how the atomic dynamics changes with temperature through the semiconductor-metal transition. The acoustic mode was clearly observed in the dynamic structure factor and its energy was determined using a damped harmonic oscillator model. The dynamical sound speed obtained by IXS for [Formula: see text] nm-1 was found to behave similarly to the temperature dependence of ultrasonic sound velocity with a minimum near the semiconductor metal transition. The results can be explained by taking liquid Se50Te50 to be an inhomogeneous liquid consisting of metallic and semiconducting domains whose size is approximately 3 nm. The relaxation time obtained from frequency dependence of the dynamical sound speed was on a picosecond time scale.

Static and dynamic structures of liquid Ba8Ga16Sn30: a melt of the thermoelectric clathrate compounds.

X-ray diffraction and inelastic x-ray scattering measurements of liquid Ba8Ga16Sn30 have been carried out to investigate local structure and atomic dynamics in the liquid. The pair distribution function shows shorter and longer interatomic distances in the first coordination shell. The dynamic structure factor exhibits the inelastic excitations on both sides of the quasielastic central peak. The inelastic excitations disperse with increasing the momentum transfer, suggesting the longitudinal acoustic mode. We found a low energy excitation in addition to the longitudinal acoustic excitation in the dynamic structure factor and it reminds us a strong relationship with a rattling motion of a guest (Ba) atom in the solid state. The temperature dependence of the pair distribution function and the longitudinal acoustic excitation energy is very weak in a range from 600 to 900 °C. The result suggests that Ba and other atoms in the melt are located around minimum positions of the effective pair potential approximated as a harmonic one.

Viscoelastic anomaly accompanying anti-crossing behaviour in liquid As2Se3.

We investigate the dynamic structure factor of the melt of the well known glass former, As2Se3, using inelastic x-ray scattering for temperatures, T, [Formula: see text] K and momentum transfers Q from [Formula: see text] nm-1. An anomaly was observed at Q = 2.7 nm-1 ([Formula: see text] K) with, in the context of a simple model, both an abrupt change in frequency and an increased linewidth reminiscent of an anti-crossing in a solid. Comparison with structural information from reverse Monte Carlo modeling of x-ray diffraction data allows us to associate the disappearance of the anomaly at higher temperatures with a drop in the number of mechanical constraints per atom, n mc, to [Formula: see text] reminiscent of the threshold applicable for glass formation in rigidity theory. It is inferred that the surprising jump in the dispersion in the liquid may be correlated with a stiffness transition in a network glass.

Transverse excitations in liquid Fe, Cu and Zn.

Transverse acoustic (TA) excitation modes were observed in inelastic x-ray scattering spectra of liquid Fe, Cu and Zn. From the analysis of current correlation functions, we concluded that TA excitation modes can experimentally be detected through the quasi-TA branches in the longitudinal current correlation spectra in these liquid metals. The microscopic elastic constants are estimated and a characteristic difference from macroscopic polycrystalline value was found in Poisson's ratio of liquid Fe, which shows an extremely softer value of ∼0.38 compared with the macroscopic value of ∼0.275. The lifetime of the TA modes were determined to be ∼0.45 ps for liquid Fe and Cu and ∼0.55 ps for liquid Zn, reflecting different interatomic correlations between liquid transition metals and non-transition metals. The propagation length of the TA modes are ∼0.85 nm in all of liquid metals, corresponding to the size of icosahedral or similar size of cages formed instantaneously in these liquid metals.

Theoretical and experimental study on two-stage-imaging microscopy using ellipsometric contrast for real-time visualization of molecularly thin films.

A two-stage-imaging ellipsometric-contrast microscope (TIEM) has been developed to measure the distribution of film thickness over a wide area of molecularly thin liquid films with a high lateral resolution, wide field of view, high thickness resolution, and high-speed. Moreover, this ellipsometric microscope enables us to achieve simultaneous measurements with other measurement apparatuses. We present the principle used to parallelize an object image to an imaging sensor and to reduce the incident angle entering the imaging sensor. In addition, we discuss the characteristic shape deformation of the object image due to oblique observation. The performance of the actual setup for TIEM was experimentally studied. A lateral resolution of about 1 µm was obtained by measuring the modulation transfer function of the TIEM. We also found that the shape deformation approximately agreed with that from theory. Furthermore, for molecularly thin films, we confirmed linearity between the film thickness and the light intensity measured with TIEM, which enables us to quantify the thickness of the films. TIEM can open up a new field of real-time imaging of thin films such as visualization of a liquid lubricant film under shear.

Transverse excitations in liquid Sn.

Transverse acoustic (TA) excitation modes were observed in inelastic x-ray scattering (IXS) spectra of liquid Sn. The excitation energies and widths of the TA modes are in good agreement with results of an ab initio molecular dynamics simulation. By comparing current correlation spectra between the experimental and theoretical results quantitatively, we have concluded that the TA modes can be detected experimentally through the quasi-TA branches in the longitudinal current correlation spectra. The lifetime and propagation length of the TA modes were determined to be ~0.7 ps and 0.8-1.0 nm, respectively, corresponding to the size of cages formed instantaneously in liquid Sn.

Histamine potentiates acid-induced responses mediating transient receptor potential V1 in mouse primary sensory neurons.

In inflamed tissues, extracellular pH decreases and acidosis is an important source of pain. Histamine is released from mast cells under inflammatory conditions and evokes the pain sensation in vivo, but the cellular mechanism of histamine-induced pain has not been well understood. In the present study, we examined the effects of histamine on [Ca(2+)](i) and membrane potential responses to acid in isolated mouse dorsal root ganglion (DRG) neurons. In capsaicin-sensitive DRG neurons from wild-type mice, acid (>pH 5.0) evoked [Ca(2+)](i) increases, but not in DRG neurons from transient receptor potential V1 (TRPV1) (-/-) mice. Regardless of isolectin GS-IB4 (IB4)-staining, histamine potentiated [Ca(2+)](i) responses to acid (>or=pH 6.0) that were mediated by TRPV1 activation. Histamine increased membrane depolarization induced by acid and evoked spike discharges. RT-PCR indicated the expression of all four histamine receptors (H1R, H2R, H3R, H4R) in mouse DRG. The potentiating effect of histamine was mimicked by an H1R agonist, but not H2R-H4R agonists and was inhibited only by an H1R antagonist. Histamine failed to potentiate the [Ca(2+)](i) response to acid in the presence of inhibitors for phospholipase C (PLC) and protein kinase C (PKC). A lipoxygenase inhibitor and protein kinase A inhibitor did not affect the potentiating effects of histamine. Carrageenan and complete Freund's adjuvant produced inflammatory hyperalgesia, but these inflammatory conditions did not change the potentiating effects of histamine in DRG neurons. The present results suggest that histamine sensitizes acid-induced responses through TRPV1 activation via H1R coupled with PLC/PKC pathways, the action of which may be involved in the generation of inflammatory pain.

Protein cysteine modifications: (1) medical chemistry for proteomics.

Protein cysteines (cysteinyl residues) play critical roles in biological processes. In the course of protein evolution under oxidizing atmosphere of the Earth, organisms have utilized highly reactive cysteines in many proteins essential for maintenance of life, i.e. enzymes, transcriptional factors, cytoskeletons, and receptors. In some enzymes, sophistical cysteine modification characterizes each catalytic mechanism. In vivo modification of protein cysteines with natural chemical compounds modulates protein functions as a molecular switch. Oxidation/reduction, thiol-disulfide exchange, nitrosylation, sulfuration, thiolation, acylation and prenylation are involved. Some protein cysteines coordinate metals or metal cofactors such as a heme or an iron sulfur cluster to form metalloproteins, serving as sensor proteins, metalloenzymes or transcriptional factors. Information on the in vitro chemical modifications and their reaction specificities of protein cysteines are essential for the investigation of the mechanisms and functions of in vivo protein cysteine modifications. In this review, we also mention historically important knowledge other than recent results on protein cysteine modification and modulation of protein function to fertilize medical proteomics.

Transverse acoustic excitations in liquid Ga.

The transverse acoustic excitation modes were detected by inelastic x-ray scattering in liquid Ga in the Q range above 9 nm(-1) although liquid Ga is mostly described by a hard-sphere liquid. An ab initio molecular dynamics simulation clearly supports this finding. From the detailed analysis for the S(Q,omega) spectra with a good statistic quality, the lifetime of 0.5 ps and the propagating length of 0.4-0.5 nm can be estimated for the transverse acoustic phonon modes, which may correspond to the lifetime and size of cages formed instantaneously in liquid Ga.

Size-selective extended X-ray absorption fine structure spectroscopy of free selenium clusters.

In a recent paper [M. Yao et al., J. Synchrotron Radiat. 8, 542 (2001)]], we proposed a new method for the size-selective EXAFS (extended x-ray absorption fine structure) of neutral-free clusters, in which not only the x-ray absorption process but also the deexcitation processes are utilized as the structural information. In order to verify this method experimentally, we have developed the synchronous measurements of EXAFS and photoelectron photoion coincidence and carried them out for a Se cluster beam by utilizing the third-generation intense x-ray source. The EXAFS spectra for Se small clusters have been obtained and compared critically with theoretical predictions.

[Whole-body MR imaging for evaluation of bone marrow cellularity in aplastic anemia].

The aim of this study was to investigate the usefulness of whole-body MRI(WB-MRI) in the evaluation of cellularity in bone marrow and the distribution of fatty marrow in aplastic anemia. WB-MRI was performed on five patients with aplastic anemia who ranged in age from 62 to 70 years of age, and on four controls with malignant lymphoma who ranged in age from 59 to 67 years. Coronal images were obtained using a body coil with an FOV of 48 cm x 48 cm, and with both fast short T1 inversion recovery(STIR) and spin-echo T1-weighted(T1-WI) in three regions: (1) head to thorax, (2) abdomen to pelvis, and (3) lower extremities. The findings on WB-MRI were compared with those of histological studies of bone marrow at the sternum and the posterior iliac crest. The results were as follows: (1) there was a correlation between the cellularity of histological studies of bone marrow and signal intensity on WB-MRI; (2) WB-MRI could detect the activity of bone marrow; and (3) in a comparison of signal intensity in aplastic anemia and control subjects, there were differences of signal intensity in the central marrow.