Atsushi Tani

Tracing the provenance of fine-grained dust deposited on the central Chinese Loess Plateau

Eolian dust deposits in north China provide an excellent means of determining past variations in continental paleoclimate and atmospheric circulation. However, debate still exists on which deserts in east Asia are the dominant sources of Chinese loess and whether the dust provenance has shifted significantly at different time scales. Here we present new constraints on the provenance of fine-grained dust deposited on the central Chinese Loess Plateau (CLP) by combining electron spin resonance signal intensity and crystallinity index of fine-grained quartz contained in samples from two loess-paleosol sequences. Our results show that the fine-grained dust deposits on the CLP originate mainly from the Gobi desert in southern Mongolia and the sandy deserts in northern China (primarily the Badain Juran and Tengger deserts), rather than from the Taklimakan desert in western China, at least during the last climatic cycle. The dominant source of fine-grained dust varied significantly, from southern Mongolia during cold periods, to northern China during warm periods. The glacial-interglacial provenance fluctuations are strongly coupled with changes in the intensity of the near-surface northwesterly winter monsoon.

Free radicals induced in aqueous solution by non-contact atmospheric-pressure cold plasma

To understand plasma-induced chemical processing in liquids, we investigated the formation of free radicals in aqueous solution exposed to different types of non-contact atmospheric-pressure helium plasma using the spin-trapping technique. Both hydroxyl radical (OH·) and superoxide anion radical (O2−·) adducts were observed when neutral oxygen gas was additionally supplied to the plasma. In particular, O2−· can be dominantly induced in the solution via oxygen flow into the afterglow gas of helium plasma. This type of plasma treatment can potentially be used in medical applications to control infectious diseases, because the O2−· is crucial for sterilization of liquids via atmospheric-pressure plasma.

Physicochemical properties of bactericidal plasma-treated water

Plasma-treated water (PTW), i.e. distilled water (DW) exposed to low-temperature atmospheric pressure helium plasma, exhibited strong bactericidal activity against Escherichia coli in suspension even within a few minutes of preparation. This effect was enhanced under acidic conditions. The bactericidal activity of PTW was attenuated according to first-order kinetics and the half-life was highly temperature dependent. The electron spin resonance (ESR) signal of an adduct of the superoxide anion radical () was detected in an aqueous solution using a spin-trapping reagent mixed with PTW, and adding superoxide dismutase to the PTW resulted in a loss of the bactericidal activity and weakening of the ESR adduct signal of in the spin-trapping. These results suggest that plays an important role in imparting bactericidal activity to PTW. Moreover, molecular nitrogen was required both in the ambient gas and in the DW used to prepare the PTW. We, therefore, suggest that the reactive molecule in PTW with bactericidal effects is not a free reactive oxygen species but nitrogen atom(s)-containing molecules that release , such as peroxynitrous acid (ONOOH) or peroxynitric acid (O2NOOH). Considering the activation energy for degradation of these species, we conclude that peroxynitric acid stored in PTW induces the bactericidal effect.

Hydrogen transfer from guest molecule to radical in adjacent hydrate-cages

Electron spin resonance measurement of gamma-ray-irradiated propane hydrates shows that the normal propyl radical withdraws hydrogen from the adjacent propane molecule through the hexagonal planes of the hydrate cage without water molecule bridging.

Electron spin resonance study on γ-ray-induced methyl radicals in methane hydrates

Electron spin resonance (ESR) studies have been performed to investigate radicals induced in ethane hydrate irradiated by γ-rays at 77 K. Two ESR spectra are observed and identified as the induced ethyl radical (g=2.0031±0.0005, Aα⊥=2.2±0.1 mT, Aα|| =2.5±0.1 mT, Aβ=2.7±0.1 mT) and induced atomic hydrogen (g=2.0026±0.0005, A=50.5±0.1 mT). From the results of ESR analysis and gas mass spectroscopy, it is concluded that the ethyl radical decays into butane by dimerization in the first-order reaction in the temperature region of 250–265 K. The activation energy of the decay reaction is 73.1±6.3 kJ/mol, which is near the dissociation enthalpy change of ethane hydrate to liquid water and gaseous ethane. This finding implies that ethane hydrate does not dissociate into ice but supercooled water in the present temperature region, similar to the dissociation of methane hydrate in our previous study.

Preparation and characterization of a new inclusion compound with a 1D molecular arrangement of organic radicals using a one-dimensional organic homogeneous nanochannel template

A new inclusion compound with a one-dimensional molecular arrangement of organic radicals (2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)) was prepared using the template compound of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) by the following two methods: i) adsorption of TEMPO vapor under vacuum at 313 K and ii) slow recrystallization in mesitylene. The arrangement of TEMPO molecules in the TPP 1D nanochannel was confirmed by thermogravimetric analysis (TG), powder XRD and ESR measurements. TEMPO molecules were accommodated in the TPP nanochannel with no decomposition, and were arranged with the orientation of the nitroxide group in the TEMPO molecule perpendicular to the axis of the nanochannel. The TPP/TEMPO inclusion compound can include TEMPO molecules up to one molecule per unit cell in the TPP crystal lattice.

Pulsed Charge Model of Fault Behavior Producing Seismic Electric Signals (SES)

The electromagnetic (EM) behavior of a geological fault is postulated to follow the mathematical model of a fault in seismology that illustrates seismic EM anomalies EMAs). Charge densities, +q and -q in C/m2 are generated at a fault zone by the change in seismic stress, α as dq/dt = -αdσ/dt - q/∊ρ, where σ,∊ and ρ are the charge generation constants measured in C/N, dielectric constant and reisitivity of bedrocks, respectively. A fault of length, 2a, plane area, A and the displacement or rupture time, τ gives pulsed charge densities, +q(t) and -q(t), or a dipole moment of P(t) = 2aAq(t) = αM0[∊ρ/(τ - ∊ρ) - exp(-t/∊ρ)] using the earthquake moment M0. Maxwells equations for this dipole in a conductive earth give power spectra of EM waves at diferrent distances. Seismic electric signals (SES) including the DC VAN method can be explained as EM waves. Electrons with density n in the atmosphere are accelerated by the electric field and travel a distance l. resulting in the exictation and ionization of atmospheric molecules leading to earthquake lightning (EQL). They also polarize the ionosphere by disturbing the transmission of EM waves prior to an earthquake and artificial electronic noises. The same pulsed field surprised eels and hamsters, suggesting seismic anomalous animal ehavious animal behavior (SAAB) as electro-physiological responses to the stimuli of electric pulses.

ESR microscopy of fossil teeth

We have used thin sections of an archaeological tooth sample to obtain spatially resolved ESR spectra using a pin-hole cavity. This study presents the first ESR images of naturally generated radiation sensitive signals. The 3-D plots of the natural and irradiated samples show strong variations of the ESR intensities within the enamel layers. Owing to the relatively large scattering of the data points it has not been possible to produce 3-D dose plots.

Pulsed ESR measurements on fossil teeth

Abstract Deconvolution of X-band spectra has shown that the signal that is used in dating studies is composed of at least three different peaks. Our measurements show that pulsed ESR can separate the axial signal from two wider peaks that are suspected of interfering with any reliable dose assessment. However, its significantly lower sensitivity prohibits the routine application of pulsed ESR in dating studies. The spin relaxation time, T 2 , of the CO 2 − centre as determined from spin echo decay curves, is in the range of about 500 to 640 ns, depending on the spin concentration.

Diagnosis of superoxide anion radical induced in liquids by atmospheric-pressure plasma using superoxide dismutase

To confirm the formation of the superoxide anion radical (O2−) in liquids by atmospheric-pressure plasma, we investigated plasma-induced radical species in water using the electron spin resonance (ESR) spin-trapping technique combined with two proteins: superoxide dismutase (SOD), which has enzymatic activity to quench the superoxide anion radical, and bovine serum albumin (BSA), which does not have this enzymatic activity. Different setups of contact and non-contact atmospheric-pressure helium plasma were tested with an additional supply of oxygen gas. For each setup of plasma, no superoxide anion adduct ESR signal was observed in the aqueous solution with SOD, whereas the ESR signal appears in the samples with BSA and without any additive proteins. This means that a superoxide anion radical in the solution is sufficiently quenched by SOD before the formation of the spin adduct. The superoxide anion radical is actually induced in an aqueous solution by atmospheric-pressure plasma when ambient gases contain oxygen.