Varying Fine-Structure Constant and the Cosmological Constant Problem

We start with a brief account of the latest analysis of the Oklo phenomenon providing the still most stringent constraint on time variability of the fine-structure constant α. Comparing this with the recent result from the measurement of distant QSO's appears to indicate a non-uniform time-dependence, which we argue to be related to another recent finding of the accelerating universe. This view is implemented in terms of the scalar-tensor theory, applied specifically to the small but nonzero cosmological constant. Our detailed calculation shows that these two phenomena can be understood in terms of a common origin, a particular behavior of the scalar field, dilaton. We also sketch how this theoretical approach makes it appropriate to revisit non-Newtonian gravity featuring small violation of Weak Equivalence Principle at medium distances. This revised version was published online in July 2006 with corrections to the Cover Date.     

Helium isotopic fingerprints of the heavy land subsidence left in groundwater of the Saga Plain,near Beppu–Shimabara graben,Kyushu, Japan

The Saga Plain is near Beppu–Shimabara graben, a region of potential active volcanism. In the graben, mantle He, which has a high ³He/⁴He ratio of 1.1 × 10⁻⁵, escapes easily from the underlying subduction zone. In groundwater of the Saga Plain, except in the Shiroishi district, this ratio gradually increased as the dissolved He content increased, to a maximum of 5 × 10⁻⁶. In central Shiroishi, however, the ratio reached a minimum of 8.7 × 10⁻⁷ with increasing dissolved He content, suggesting that groundwater in central Shiroishi has selectively accumulated radiogenic He, which has a very low ratio of 1 × 10⁻⁸, rather than reflecting the regional He, which is rich in mantle He. This can be explained if groundwater in Shiroishi has become mixed with fossil pore water drawn from impermeable marine clay aquitard layers. The withdrawal of pore water has also caused severe land subsidence in central Shiroishi.     

Dissakisite-(Ce) chemical composition: some implications for its origins

Euhedral dissakisites from Trimouns dolomite mine, France, is compositionally zoned. Back-scattered electron (BSE) images reveal that each of the described dissakisite crystals has three distinct compositional zones: normal zoned core (Mg-rich), oscillatory zoned middle (Ca–Al-rich) and homogeneous rim (Fe–ΣREE-rich). The latter zone with Fe²⁺ > Mg corresponds to allanite-(Ce). Dissakisite-(Ce) also displays pronounced zoning in Fe/Mg which may suggest that the temperature of crystallization continuously decreased from core to rim. Despite a systematic increase in Fe/Mg of the dissakisite with an allanite rim, there is no monotonic decrease in the REE zoning: the normal zoned core and homogeneous rim are rich in La, Ce and Pr, but the relatively REE-poor oscillatory zoned middle is relatively abundant in Y, Sm and Gd. Discontinuous variation in REE content of the dissakisite, with the allanite rim may indicate a localized change in either the relative concentration of various ligands or pH of the crystallizing fluid. Observations under the polarizing microscope confirm that the different zones have simultaneous extinction. These chemical and optical observations suggest that epitaxial crystallization of dissakisite, from Trimouns, passes through three formation stages. The ternary Fe²⁺–Mg²⁺–(Al + Fe)³⁺ diagram illustrates that in general dissakisite can be classified into two groups, (Al + Fe)³⁺-rich and an Mg-rich; dissakisite from Trimouns belongs to the former group. Chondrite-normalized REE patterns of dissakisites from Trimouns are similar to those of allanites formed by hydrothermal fluids. In conclusion, it is clear from the above two geochemical characteristics that dissakisites from Trimouns are of (Al + Fe)³⁺-type, and were derived from hydrothermal fluids.     

Crystal chemistry of volcanic allanites indicative of naturally induced oxidation-dehydrogenation

The crystal chemistry of volcanic allanites from both the Youngest Toba Tuff (YTT), Sumatra, Indonesia and SK100 volcanic ash beds (SK100-VAB), Niigata, Japan has been examined by electron microprobe analysis (EMPA), Fourier-transform infrared spectroscopic analysis (FTIR), and single-crystal structure analysis. In the FTIR study, based on the Diamond ATR accessory, YTT and SK100- VAB allanites were observed to have different OH contents, respectively: the former has 0.64 wt% H₂O (OH: 0.40 apfu.), while the latter has 1.65 wt% H₂O (OH: 1.00 apfu.). The crystal structures of these two allanites have been refined to individual R indices (3.64 and 4.25) based on 1350 observed reflections (|Fo| > 4sig|Fo|) measured using a single-crystal diffractometer with MoKα X-radiation. The OH-poor YTT allanite has a shorter b axis, a longer c axis, and larger β value than the relatively OH-rich SK100-VAB one. The bond valence sums of O4 (accepter oxygen for H atom) and O10 (donor oxygen for H atom) are 1.962 and 1.709 v.u. for YTT allanite (valence sum: 3.671 v.u.) and 1.754 and 1.271 v.u. for SK100-VAB one (valence sum: 3.025 v.u.). The difference from the ideal total bond valence value (4.00 v.u.) of O4 and O10 in YTT allanite (0.33 v.u.) is smaller than that in SK100-VAB (0.98 v.u.). These difference values are also broadly consistent with the corresponding differences in OH content between the YTT (OH: 0.40 apfu.) and SK100-VAB allanites (OH: 1.00 apfu.) determined by FTIR- ATR. Chemical analyses, FTIR-ATR and crystal structure refinement of YTT and SK100-VAB allanites yielded the following crystal chemical formula: YTT: (Ca_0.83Mn²⁺ _0.06Fe²⁺ _0.11)(La_0.24Ce_0.32Pr_0.04Nd_0.11Sm_0.02Th_0.04Ca_0.21)(Al_0.73Fe³⁺ _0.19Ti_0.08)(Al_0.89Fe³⁺ _0.11)(Fe²⁺ _0.22Fe³⁺ _0.62Mg_0.16)(SiO₄)Si₂O₇O_1.6(OH)_0.4, SK100-VAB: (Ca_0.81Fe²⁺ _0.13Mn²⁺ _0.06)(La_0.22Ce_0.34Pr_0.05Nd_0.13Sm_0.02Th_0.02Ca_0.22)(Al_0.76Fe³⁺ _0.19Ti_0.05)Al_1.00(Fe²⁺ _0.73Fe³⁺ _0.17Mg_0.10)(Si_0.96Al_0.04O₄)Si₂O₇O(OH). Therefore, it is concluded that welding of the Youngest Toba Tuff caused the following post-crystallization changes to occur in YTT allanite: oxidation of Fe²⁺ to Fe³⁺, release of H₂, and the concomitant replacement of OH^? by O^2?. These oxidation and dehydrogenation processes advanced during the welding to thereby produce oxyallanite. Oxyallanite had been reported only in laboratory studies where it was produced by heating natural allanite. Our report on natural oxyallanite suggests that it may be present in other welded silicic volcanic rocks as well.     

Antifouling herbicides in the coastal waters of western Japan

Residue analyses of some antifouling herbicides (Diuron, Irgarol 1051 and the latter's degradation product M1, which is also known as GS26575), were conducted in waters collected along the coast of western Japan. In total, 142 water samples were collected from fishery harbours (99 sites), marinas (27 sites), and small ports (16 sites) around the Seto Inland Sea, the Kii Peninsula, and Lake Biwa, in August 1999. A urea-based herbicide, Diuron, was positively identified for the first time in Japanese aquatic environments. Diuron was detected in 121 samples (86%) up to a highest concentration of 3.05 microg/l, and was found in 86% of samples from fishery harbours, 89% from marinas, and 75% from ports. Four freshwater samples out of 11 collected at Lake Biwa contained Diuron. Neither Irgarol 1051 nor M1 was found in the lake waters, but both were found in many coastal waters. Irgarol 1051 was found in 84 samples (60%) at a highest concentration of 0.262 microg/l. The concentrations detected were of similar magnitude to those in our previous surveys, taken in 1997 and 1998. M1 was found in 40 samples (28%) up to a highest concentration of 0.080 microg/l. The concentrations detected were generally lower than those found in our previous surveys. The detection frequency among fishery harbours, marinas, and ports was 57-70% for Irgarol 1051 and 25-30% for M1. Ninety-five per cent of the coastal waters in which M1 was detected also contained Irgarol 1051, and 93% of the samples in which Irgarol 1051 was detected also contained Diuron. These results clearly suggest that commercial ship-bottom paints containing both Diuron and Irgarol 1051 are used extensively in the survey area.     

Dynamical structure and wind-driven upwelling in a summertime anticyclonic eddy within Funka Bay,Hokkaido, Japan

We conducted hydrographic observations in 2002 to investigate the anticyclonic eddy that emerges every summer in Funka Bay, Hokkaido, Japan, and elucidate dynamical structure and wind-driven upwelling within the eddy. The anticyclonic eddy has a vertical scale of 32 m and is characterized by a strong baroclinic flow and a sharp pycnocline with a concave isopycnal structure. The sharp pycnocline occurs below a warm and relatively low-salinity water termed summer Funka Bay water (FS), which is formed by heating from solar radiation and dilution from river discharge in summertime Funka Bay. Flow of the anticyclonic eddy rotates as a rigid body at each layer, and the horizontal scale and rotation period of the eddy in the surface layer are about 15 km and 2.2 days, respectively. The dynamical balance of the anticyclonic eddy is well explained by the gradient flow balance. The contribution of centrifugal force to the gradient flow balance is about 27%. Therefore, the effect of the nonlinear term associated with centrifugal force cannot be neglected in considering the dynamics of the anticyclonic eddy in summertime Funka Bay. In addition, upwelling of subsurface water was observed in the surface layer of the central part of the eddy. The formation mechanism of this upwelling is consistent with interaction between horizontal uniform wind and the eddy. This upwelling is driven by upward Ekman pumping velocity related to the horizontal divergence of Ekman transport. In summertime Funka Bay, there are two wind effects that affect the anticyclonic eddy: a decay effect of the upwelling of subsurface water resulting from horizontal uniform wind (mainly northwesterly wind), and a maintenance or spin-up effect of horizontal non-uniform wind (mainly southerly–southeasterly seasonal wind) with negative wind stress curl.     

Crustal structure and tectonics of the Hidaka Collision Zone, Hokkaido (Japan), revealed by vibroseis seismic reflection and gravity surveys

This study is the first integrated geological and geophysical investigation of the Hidaka Collision Zone in southern Central Hokkaido, Japan, which shows complex collision tectonics with a westward vergence. The Hidaka Collision Zone consists of the Idon'nappu Belt (IB), the Poroshiri Ophiolite Belt (POB) and the Hidaka Metamorphic Belt (HMB) with the Hidaka Belt from west to east. The POB (metamorphosed ophiolites) is overthrust by the HMB (steeply eastward-dipping palaeo-arc crust) along the Hidaka Main Thrust (HMT), and in turn, thrusts over the Idon'nappu Belt (melanges) along the Hidaka Western Thrust (HWT). Seismic reflection and gravity surveys along a 20-km-long traverse across the southern Hidaka Mountains revealed hitherto unknown crustal structures of the collision zone such as listric thrusts, back thrusts, frontal thrust-and-fold structures, and duplex structures. The main findings are as follows. (1) The HMT, which dips steeply at the surface, is a listric fault dipping gently at a depth of 7 km beneath the eastern end of the HMB, and cutting across the lithological boundaries and schistosity of the Hidaka metamorphic rocks. (2) A second reflector is detected 1 km below the HMT reflector. The intervening part between these two reflectors is inferred to be the POB, which is only little exposed at the surface. This inference is supported by the high positive Bouguer anomalies along the Hidaka Mountains. (3) The shallow portion of the IB at the front of the collision zone has a number of NNE-dipping reflectors, indicative of imbricated fold-and-thrust structures. (4) Subhorizontal reflectors at a depth of 14 km are recognized intermittently at both sides of the seismic profile. These reflectors may correspond to the velocity boundary (5.9–6.6 km/s) previously obtained from seismic refraction profiling in the northern Hidaka Mountains. (5) These crustal structures as well as the back thrust found in the eastern end of the traverse represent characteristics of collisional tectonics resulting from the two collisional events since the Early Tertiary.