Investigation of the relationship between optical auroral forms and HF radar E region backscatter

The SuperDARN HF radars have been employed in the past to investigate the spectral characteristics of coherent backscatter from L-shell aligned features in the auroral E region. The present study employs all-sky camera observations of the aurora from Husafell, Iceland, and the two SuperDARN radars located on Iceland, Þykkvibær and Stokkseyri, to determine the optical signature of such backscatter features. It is shown that, especially during quiet geomagnetic conditions, the backscatter region is closely associated with east-west aligned diffuse auroral features, and that the two move in tandem with each other. This association between optical and radar aurora has repercussions for the instability mechanisms responsible for generating the E region irregularities from which radars scatter. This is discussed and compared with previous studies investigating the relationship between optical and VHF radar aurora. In addition, although it is known that E region backscatter is commonly observed by SuperDARN radars, the present study demonstrates for the first time that multiple radars can observe the same feature to extend over at least 3 h of magnetic local time, allowing precipitation features to be mapped over large portions of the auroral zone.     

Incorporation of incomplete fault-slip data into stress tensor inversion

A fault-slip datum used in the stress tensor inversion techniques is composed of fault orientation, slip orientation and the sense of slip. Sometimes the latter two items are not available. This paper proposes a method to deal with such incomplete fault-slip data. Firstly, the constraints on stress state from full and incomplete data are theoretically specified. The admissible stresses are expressed by the probability distributions in the parameter space. The objective function of inversion is given by superposing the probability distributions for all data including full and incomplete ones. Finally, the peaks of the objective function are detected to enumerate possible solutions. The validity of the present method is tested by simulated data. The incorporation of incomplete data can enhance the detectability of stress states and expands the applicability of stress tensor inversion.     

Effect of atmospheric humic-like substances on the enhanced dissolution of volatile organic compounds into dew water

Simultaneous sampling of chlorinated hydrocarbons (CHs) and monocyclic aromatic hydrocarbons (MAHs), potentially harmful to humans and/or responsible for the formation of ozone and secondary particles, in dew water and in the ambient air was carried out from August 2004 to July 2005 in Hino City, situated in the western part of Greater Tokyo, Japan. CHs were less contained in dew water than MAHs. Toluene (volume-weighted mean concentration, VWM: 4.77 nM) and m,p-Xylenes (VWM: 5.07 nM) except dichloromethane, which was abnormally high (VWM: 1.14 μM), were abundant among eleven VOCs determined in dew water. Chloroform, carbon tetrachloride, 1,2-dichloroethane, and benzene were not detected in dew water during the study period. Dew water contained higher amounts of VOCs than would have been expected from the ambient gas-phase concentrations and the temperature-corrected Henry's law constants. Following the determination method of humic substances in river water proposed by Hiraide et al. [Hiraide, M., Shima, T., Kawaguchi, H., 1994. Separation and determination of dissolved and particulate humic substances in river water. Mikrochim. Acta 113, 269–276], the VWM of soluble humic and fulvic acid fractions in dew water was found to be 1.00 mg/L and 0.87 mg/L (n = 20), respectively, while the VWM of particulate humic and fulvic acid fractions was found to be 0.61 mg/L and 0.42 mg/L (n = 20), respectively. Surface tension decreased with an increase in dissolved fulvic acid fraction in dew water, indicating that humic-like substances with relatively lower molecular weight, which is soluble in acid solution, could be an effective surface-active species within dew water. The enrichment factors, which were defined as the ratio of the observed VOCs concentration to the estimated, were over 10² for MAHs except for benzene and increased as the increment of total humic-like substances (HULIS) concentration (the sum of humic and fulvic acid fractions in both dissolved and particulate form) normalized by total inorganic ion concentration in dew water. Our results indicate that total HULIS in dew water could enhance the dissolution of atmospheric VOCs into dew droplets.     

Uptake of selenium and other oxyanionic elements in marine ferromanganese concretions of different origins

The concentration of selenium in marine ferromanganese concretions varies between 0.02 and 1.2 mg kg⁻¹, with an average of 0.6 mg kg⁻¹. This is about two orders of magnitude lower than previously reported. In contrast to minor cationic elements, the concentrations of selenium are relatively uniform between ferromanganese concretions of different origins, except for hydrothermal crusts. It shows the same trends of element enrichment as other oxyanionic elements. The incorporation of selenium into ferromanganese concretions is attributed to adsorption of selenate on iron and manganese oxides.     

埃及阿赫米姆古墓遗址浅层地球物理勘查

Ground penetrating radar, electromagnetic terrain conductivity, and electric tomography have proven to be effective tools if they are combined together to investigate archeological sites. We have conducted a geophysical survey at the Akhmim archaeological site, the main objective of our survey is to locate additional buried structures for further excavation. Geophysical data were acquired in the area using the GEM-300 multi-frequency terrain conductivity profiler, the SIR 2000 ground penetrating radar, and the Syscal R2 resistivity meter systems. The results of the integrated interpretation show a number of buried features and a strong linear zone about 1 m wide that coincides with the suspected trend of a buried wall. There appears to be two parallel ridges of strong reflections on either side, indicating two parallel walls extended East-West and a room is identified at the bottom left comer of the site. Moreover, the interpretation results of some selected GPR and dipoledipole resistivity profiles adjacent to the open-air museum suggest the existence of a second statue of Ramses Ⅱ to the right of the previously discovered statue which could still be buried in the sand.     

Experimental calibration of sapphirine–spinel Fe–Mg exchange thermometer: Implication for constraints on P–T condition of Howard Hills, Napier Complex, East Antarctica

The Fe²⁺–Mg distribution coefficients between sapphirine and spinel:

were experimentally determined at pressures of 9–13 kbar and temperatures of 950–1150 °C using a natural ultrahigh-temperature (UHT) granulite with paragenesis of these minerals from the Napier Complex in East Antarctica [X_Mg = Mg / (Fe + Mg); X_Fe = Fe / (Fe + Mg)]. A new sapphirine–spinel geothermometer has been obtained as:

We applied the exchange thermometer to UHT or high-grade metamorphic rocks that were reported from various complexes in the world. If the K_D values of 2.63–4.34 obtained from low-Cr mineral pairs such as X_Cr^Spr < 0.016 and X_Cr^Spl < 0.047 were substituted into the equation, their temperature conditions would be estimated as 806–1050 °C at 11 kbar. The X_Cr means Cr / (Al + Cr(+ Fe³⁺)). These temperatures are reasonable retrograde or near peak metamorphic condition.     

Generation of tidal bedding in a circular flume experiment: formation process and preservation potential of mud drapes

Flume experiments aimed to produce flaser bedding were conducted using fine sand and clay in a circular flume. The formation process of mud drapes during the slack-water stage was revealed in detail. When the tidal current declines, a uniform mobile mud layer initially settles from suspension and drapes the entire rippled sand bed (type A mud). When the remaining flow velocity is very low, a more fluid mud begins to settle out (type B mud) that preferentially fills the ripple troughs, the ripples and mud together forming a flat surface. At slack tide, the two-phase mud drape is temporarily stationary. After the onset of the reversed flow phase, most of the type B mud is resuspended, while the type A mud is eroded from the crests, leaving behind a remnant mud drape (flaser) in the troughs that is subsequently buried by migrating ripples. Type B mud generally contains variable amounts of sand derived from eroded ripple crests, but does not show any visible internal sedimentary structures. Type A mud represents the ‘mud drapes’ commonly described in the literature, the temporary existence of type B mud having gone unnoticed because of its low preservation potential. When present, it can be recognized by its sand content and the occurrence of flame structures in ripple troughs. Tidal deposits reflecting the existence and depositional characteristics of both type A and type B mud are found in, for example, the macrotidal Oligocene Ashiya Group, Japan.     

Climatic physical snowpack properties for large-scale modeling examined by observations and a physical model

Here we have conducted an integral study using site observations and a model with detailed snow dynamics, to examine the capability of the model for deriving a simple relationship between the density and thermal conductivity of the snowpack within different climatic zones used in large-scale climate modeling. Snow and meteorological observations were conducted at multiple sites in different climatic regions (two in Interior Alaska, two in Japan). A series of thermal conductivity measurements in snow pit observations done in Alaska provided useful information for constructing the relationship. The one-dimensional snow dynamics model, SNOWPACK, simulated the evolution of the snowpack and compared observations between all sites. Overall, model simulations tended to underestimate the density and overestimate the thermal conductivity, and failed to foster the relationship evident in the observations from the current and previous research. The causes for the deficiency were analyzed and discussed, regarding a low density of the new snow layer and a slow compaction rate. Our working relationships were compared to the equations derived by previous investigators. Discrepancy from the regression for the melting season observations in Alaska was found in common.     

Barium Increasing Prior to Opal during the Last Termination of Glacial Ages in the Okhotsk Sea Sediments

Ba and Ti in a sediment core (10 m long) from the Okhotsk Sea, covering the last 120 kyrs, were measured. The authigenic Ba (Ba_ex) contents were calculated and compared with the opal. The correlation coefficient between Ba_ex and opal was quite small (r = 0.34), but it greatly grew larger (r = 0.90), if the Ba_ex contents were multiplied by a simple function increasing with depth, except for two intervals. This may be due to the gradual change in the sedimentation environment during the glacial ages. One of the exceptional interval is found at 60–170 cm in depth, corresponding to 10–17 calendar kyr ago, the last termination period of glacial ages, where the Ba_ex began to increase prior to opal. Since the calcium carbonate contents similarly increased prior to the opal increase, the Ba_ex may be also related to calcareous organisms besides siliceous ones. The other is the last interglacial period around 120 kyr ago when the opal contents were high, but those of the Ba_ex were not increased. This can be explained, if the Ba_ex was reduced to sulfide and dissolved away in a strongly anoxic environment during the biologically productive period. During the glacial ages, the mass accumulation rate (MAR) of lithogenic Ti was about twice the amount of that during the interglacial ages. For opal, however, the contrast between the glacial and interglacial ages was more remarkable in its MAR than in its concentration in sediments, due to the larger variation in the bulk sedimentation rates. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydrostatic compression of ilmenite phase of ZnSiO3 and MgGeO3

Accurate measurements of cell parameters were performed on the ilmenite phases of ZnSiO₃ and MgGeO₃ using an X-ray diffraction method under hydrostatic conditions. The linear changes in cell parameter are represented by 1?a/a ₀=(1.06±0.04)×10^?4 P(kbar) and 1?c/c ₀=(2.11±0.04)×10^?4 P for ZnSiO₃, and 1?a/a ₀=(1.37±0.03)×10^?4 P and 1?c/c ₀=(2.05±0.04)×10^?4 P for MgGeO₃. A least-squares calculation using the first-order Birch-Murnaghan equation gives K _T =2.16±0.02 Mbar and K _T =1.87±0.02 Mbar for ZnSiO₃ and MgGeO₃, respectively. Elastic systematics assuming K _T V _m =constant give a predicted value K _T =2.14 Mbar for the ilmenite phase of MgSiO₃.