ASCA Observation of the Lyman-limit Quasar PKS2145+067

X-ray observation of a famous Lyman-limit quasar PKS2145+067at z_em= 0.990 was carried with ASCA. The source showed a 2-10 keV flux of 1.3 E-11 erg cm^-2 sec^-1 (L_X = 2.5 E46 erg sec^-1 for H_0=50 km s^-1 Mpc^-1) described by a power-law spectrum with a photon index Gamma=1.63 +/- 0.04 . In the ASCA energy band, no excess absorption was detected implying the absorption column density at z_ ab=0.791 was less than 1.6 E21 cm^-2 if absorbing medium had a metal abundance of 0.5 solar. Comparison with previous Einstein and ROSAT observations shows that PKS2145+067 has increased its luminosity by a factor of 2--3 between 1991 and 1998.Comment: 15 pages, 3figures, Latex(PASJadd,sty, PASJ95.sty) accepted in PAS

Polytypes of long-period stacking structures synchronized with chemical order in a dilute Mg-Zn-Y alloy

A series of structural polytypes formed in an Mg-1at.%Zn-2at.%Y alloy has been identified, which are reasonably viewed as long-period stacking derivatives of the hcp Mg structure with alternate AB stacking of the close-packed atomic layers. Atomic-resolution Z-contrast imaging clearly revealed that the structures are long-period chemical-ordered as well as stacking-ordered; unique chemical order along the stacking direction occurs as being synchronized with a local faulted stacking of AB'C'A, where B' and C' layers are commonly enriched by Zn/Y atoms.Comment: 8 pages, 4 figures; submitted to Philosophical Magazine Letter

Electric Control of Spin Helicity in a Magnetic Ferroelectric

Magnetic ferroelectrics or multiferroics, which are currently extensively explored, may provide a good arena to realize a novel magnetoelectric function. Here we demonstrate the genuine electric control of the spiral magnetic structure in one of such magnetic ferroelectrics, TbMnO3. A spin-polarized neutron scattering experiment clearly shows that the spin helicity, clockwise or counter-clockwise, is controlled by the direction of spontaneous polarization and hence by the polarity of the small cooling electric field.Comment: 4 pages, 3 figure

ASCA Measurements of Metallicity and Temperature Distributions in Three Clusters: A4059, MKW 3s and 2A 0335+096

We present ASCA results on the distributions of metallicity and temperature in 3 bright near-by clusters: A4059, MKW 3s and 2A 0335+096. A significant gradient in the metal abundance is detected in A4059, while other clusters suggest similar gradients with low significance. These features together with recent results on AWM 7 and Perseus clusters suggest that metals injected in the ICM are not effectively mixed in the cluster space. Analysis of the GIS data, without explicitly including the cooling flow model, shows no substantial temperature drop at large radii (at half the virial radii) for the 3 systems. This is contrary to the recent results for 30 clusters by Markevitch et al. (1998) who assume rather strong cooling flows. The gas mass fraction of these clusters are 10-15% within 1 Mpc, which suggests that baryonic fraction of about 20% including the stellar mass is a common level in galaxy groups and clusters.Comment: 25 pages, 21 figures; accepted by PASJ; uses PASJ95.sty, PASJ2.sty, and PASJadd.st

Taxonomic study of the genus Myrmarachne of Borneo (Araneae: Salticidae)

Twenty-two species of the genus Myrmarachne are reported from Borneo in the present study. Among those, eight are new to science, M. acromegalis sp. nov., M. alticephalon sp. nov., M. brevichelicera sp. nov., M. crassembolus sp. nov., M. cyrtodens sp. nov., M. endoi sp. nov., M. lambirensis sp. nov. and M. sabahna sp. nov. The following synonymies are proposed: Myrmarachne topali Zabka, 1985 syn. nov. as a junior synonym of M. hanoii Zabka, 1985, M. gigantea Zabka, 1985 syn. nov. as a junior synonym of M. maxillosa (C. L. Koch, 1846). The females of M. assimilis Banks, 1930, M. biseratensis Badcock, 1918, M. gedongensis Badcock, 1918, M. markaha Barrion & Litsinger, 1995 and M. shelfordii Peckham & Peckham, 1907 are described for the first tim

Anomalous Coexistence of Ferroelectric Phases (P∥aP\parallel a and P∥cP\parallel c) in Orthorhombic Eu1−y_{1-y}Yy_yMnO3_3 (y>0.5y>0.5) Crystals

We have investigated the magnetic and dielectric properties of orthorhombic Eu$_{1-y}$Y$_y$MnO$_3$ ($0\leq y\leq 0.6$) single crystals without the presence of the 4$f$ magnetic moments of the rare-earth ions. In $y\geq 0.2$, the magnetic-structure driven ferroelectricity is observed. The ferroelectric transition temperature is steeply reducing with increasing $y$. In $y\geq 0.52$, two ferroelectric phases ($P\parallel a$ and $P\parallel c$) are coexistent at low temperatures. In these phases, ferroelectricity has different origin, which is evidenced by the distinctive poling-electric-field dependence of electric polarization. Namely, the electric polarization along the c axis ($P_c$) is easily saturated by a poling electric field, therefore $P_c$ is caused by the $bc$ spiral antiferromagnetic order. On the other hand, the electric polarization along the a axis ($P_a$) is probably attributed to the collinear $E$-type antiferromagnetic order, because $P_a$ is unsaturated even in a poling field of $10^6$ V/m.Comment: 10 pages, 4figures, to be published in Journal of the Physical Society of Japa

The 1996 U.S. Purse Seine Fishery for Tropical Tunas in the Central-Western Pacific Ocean

The U.S. tropical tuna purse seine fleet has fished the central-western Pacific Ocean under the South Pacific Tuna Treaty since 1988. The 1996 fishery was the poorest since the start ofthe Treaty. Fishing effort declined due to the financial collapse of a large fishing enterprise. Catches reached record lows for yellowfin tuna, Thunnus albacares, and skipjack tuna, Katsuwonus pelamis, and continued a declining trend that started in 1995. Catch rates also decreased to the lowest levels since 1991. Whether this declining trend in catch rates is due to reduced availability of fish caused by cyclic ocean environmental changes affecting vulnerability or to reduced abundance from excessive fishing pressure is not yet known and needs to be assessed