A chemical sequence of macromolecular organic matter in the CM chondrites

Abstract— A new organic parameter is proposed to show a chemical sequence of organic matter in carbonaceous chondrites, using carbon, hydrogen, and nitrogen concentrations of solvent‐insoluble and high‐molecular weight organic matter (macromolecules) and the molecular abundance of solvent‐extractable organic compounds. The H/C atomic ratio of the macromolecule purified from nine CM chondrites including the Murchison, Sayama, and seven Antarctic meteorites varies widely from 0.11 to 0.72. During the H/C change of ?0.7 to ?0.3, the N/C atomic ratio remains at ?0.04, followed by a sharp decline from ?0.040 to ?0.017 between H/C ratios from ?0.3 to ?0.1. The H/CN/C sequence shows different degrees of organic matter thermal alteration among these chondrites in which the smaller H/C‐N/C value implies higher alteration levels on the meteorite parent body. In addition, solvent‐extractable organic compounds such as amino acids, carboxylic acids, and polycyclic aromatic hydrocarbons are abundant only in chondrites with macromolecular H/C values >?0.5. These organic compounds were extremely depleted in the chondrites with a macromolecular H/C value of <?0.5. Possibly, most solvent‐extractable organic compounds could have been lost during the thermal alteration event that caused the H/C ratio of the macromolecule to fall below 0.4.     

Collapse of low-mass clouds in the presence of a UV radiation field

The collapse of marginally Jeans-unstable primordial gas clouds in the presence of a UV radiation field is discussed. Assuming that the dynamical collapse proceeds approximately in an isothermal self-similar fashion, we investigate the thermal evolution of the collapsing central core until H₂ cooling dominates photoheating and the temperature drops to below 10⁴ K. Consequently, the mass of the cooled core is evaluated as M _cool=3.6×10⁶ M_⊙ ( I ₂₁/1)^−0.32. This scale depends only on the incident UV intensity, and provides a lower limit to the mass of collapsed objects in the UV radiation field.     

The location and size of a solar hard X-ray burst on September 27, 1969

The location and size of a solar impulsive hard X-ray burst have been determined in one dimension to a considerable precision with a balloon-borne X-ray modulation collimator. The center of the X-ray source is on the line passing through the center of a big H flare region of 3 arc min. The size of the X-ray source is remarkably smaller and may be one arc min or less.     

Application of underwater optical data to estimation of primary productivity

We conducted time-series observations of optical fields near the base of the euphotic zone (approximately 40 m) using moored automatic optical sensors at a time-series station in the Western Pacific Subarctic Gyre from March 2005 to July 2006 (with some gaps). We used the ratio of photosynthetically available radiation at the surface (surface PAR) to in situ quantum irradiance (in situ QI) at about 40 m as an index of opacity (surface PAR/in situ QI), which began to increase in the middle of April and peaked between the end of June and the middle of July 2005. This ratio then decreased toward winter. The ratio increased again beginning in January 2006, and large peaks were observed in June and July 2006. As an index of chlorophyll abundance we used the ratio of spectral irradiance at wavelengths of 555 and 443 nm (Ed₅₅₅/Ed₄₄₃) at about 40 m; seasonal variability of this ratio synchronized well with the attenuation coefficient “k” estimated with surface PAR, in situ QI, and BLOOMS depth. We estimated primary productivity (PP) using Ed₅₅₅/Ed₄₄₃ and an empirical equation based on a previous model but improved on the basis of shipboard observations. Estimated PP agreed well with observed PP. Seasonal variability of estimated PP was synchronized with that of organic carbon flux observed by sediment traps from approximately 150, 540, 1000, and 5000 m. This study demonstrates that time-series observations of in situ optical fields could contribute to the estimation of primary productivity and the study of the biological pump in the ocean.     

XMM observations of the high-redshift quasar RX J1028.6 – 0844 at z= 4.276 : soft X-ray spectral flattening

We present results from a new XMM–Newton observation of the high-redshift quasar RX J1028.6 – 0844 at a redshift of 4.276. The soft X-ray spectral flattening, as reported by a previous study with ASCA , is confirmed to be present, with, however, a reduced column density when modelled by absorption. The inferred column density for absorption intrinsic to the quasar is  2.1(^+0.4_−0.3) × 10²²  cm⁻²  for cold matter, and higher for ionized gas. The spectral flattening shows remarkable similarity with that of two similar object, namely GB 1428 + 4217 and PMN J0525 − 3343. The results improve upon those obtained from a previous short-exposure observation for RX J1028.6 – 0844 with XMM–Newton . A comparative study of the two XMM–Newton observations reveals a change in the power-law photon index from  Γ≃ 1.3  to 1.5 on time-scales of about one year. A tentative excess emission feature in the rest-frame 5–10 keV band is suggested, which is similar to that marginally suggested for GB 1428 + 4217.     

Variability in Active Galactic Nuclei

AGN (Active Galactic Nuclei) have their profound time variability over a wide range of time scales. Although many results of AGN variability have been provided from wide band wavelength observations, I would like to concentrate the recent problems concerning a nearby region of their central engine based on the X-ray observations which are most efficient to investigate this region. In this paper we will investigate mainly the result of Seyfert galaxies which would be generalized to other AGN.     

Dinoflagellate Cysts in Surface Sediments from Southern Coast of Korea

To investigate the distributions of dinoflagellate cysts in relation to environmental conditions from southern coast of Korea, surface sediment samples collected from 11 stations in Gamak Bay, Yeoja Bay and the offshore area of Yeoja Bay were analyzed. Dinoflagellate cyst assemblages observed in the study area included many species commonly reported from other temperate regions. Among them, Polykrikos cysts were dominant, together with Brigantedinium spp. and Spiniferites spp. Based on cluster analysis, dinoflagellate cyst assemblages were divided into two main groups; group I, located in Yeoja Bay and group II, located in Gamak Bay and the offshore area of Yeoja Bay. Principal component analysis identified differences in salinity levels as the main environmental factors affecting the distributional characteristics of dinoflagellate cyst assemblages in the study area. Gamak Bay is a typical eutrophied area as result of extensive human activities around the bay, and heterotrophic cysts, including Polykrikos cysts, are remarkably abundant and likely to be a useful indicator for eutrophication in Gamak Bay.     

Evaluation of spatial correlation between nutrient exchange rates and benthic biota in a reef-flat ecosystem by GIS-assisted flow-tracking

A Geographic Information System (GIS)-aided flow-tracking technique was adopted to investigate nutrient exchange rates between specific benthic communities and overlying seawater in a fringing reef of Ishigaki Island, subtropical Northwestern Pacific. Net exchange rates of NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, PO₄ ³⁻, Total-N and Total-P were estimated from concentration changes along the drogue trajectories, each of which was tracked by the Global Positioning System and plotted on a benthic map to determine the types of benthic habitat over which the drogue had passed. The observed nutrient exchange rates were compared between 5 typical benthic zones (branched-coral (B) and Heliopora communities (H), seaweed-reefrock zone (W), bare sand area (S), and seagrass meadow (G)). The dependence of nutrient exchange rates on nutrient concentrations, physical conditions and benthic characteristics was analyzed by multiple regression analysis with the aid of GIS. The spatial correlation between nutrient exchange rates and benthic characteristics was confirmed, especially for NO₃ ⁻ and PO₄ ³⁻, which were usually absorbed in hydrographically upstream zones B and W and regenerated in downstream zones H and G. NO₃ ⁻ uptake in zones B and W was concentration-dependent, and the uptake rate coefficient was estimated to be 0.58 and 0.67 m h⁻¹, respectively. Both nutrient uptake in zone W and regeneration in zone H were enhanced in summer. The net regeneration ratio of NO₃ ⁻/PO₄ ³⁻ in zone H in summer ranged 5.2 to 34 (mean, 17.4), which was somewhat higher than previously measured NO₃ ⁻/PO₄ ³⁻ for sediment pore waters around this zone (1.1–8.5). Nutrient exchanges in zone S were relatively small, indicating semi-closed nutrient cycling at the sediment-water interface of this zone. NH₄ ⁺ efflux from sediments was suggested in zone G. The data suggest that the spatial pattern of nutrient dynamics over the reef flat community was constrained by zonation of benthic biota, and that abiotic factors such as nutrient concentrations and flow rates, influenced nutrient exchange rates only in absorption-dominated communities such as zones B and W.     

Laboratory frost sorting by needle ice: a pilot experiment on the effects of stone size and extent of surface stone cover

Sorted patterned ground is ubiquitous where gravelly fine soil experiences freeze–thaw cycles, but experimental studies have rarely been successful in reproducing such patterns. This article reports an attempt to reproduce miniature sorted patterns by repeating needle‐ice formation, which simulates frost sorting in regions dominated by diurnal freeze–thaw cycles. Six full‐scale laboratory models were tested. They consisted of near‐saturated volcanic fine soil topped by small stones of uniform size; the models explored a range of stone size (~6, ~12, ~17 and ~22 mm) and surface abundance (20, 40 and 60% cover). The stones were placed in a grid on the surface. These models were subjected to 20–30 temperature excursions between 10 °C and ?5 °C in 12 hours. The evolution of surface patterns were visually traced by photogrammetry. A data logging system continuously monitored vertical soil displacements, soil temperatures and moistures at different depths. All experimental runs displayed needle‐ice formation (2–3 cm in height) and resulting displacement of stones. The soil domains tended to heave faster and higher than the stones, leading to outward movement of the former and concentration of the stones. In plan view, smaller stones showed relatively fast and long‐lasting movements, while larger stones stabilized after the first five cycles. The 20% stone cover produced stone islands, whereas the 40% cover resulted in sorted labyrinths (a circle‐island complex) that may represent incipient sorted circles. The average diameter or spacing of these forms are 12–13 cm, being comparable to those in the field. The experiments imply that needle‐ice activity promotes rapid formation of sorted patterns, although the formation of well‐defined sorted circles may require hundreds of diurnal frost heave cycles. Copyright © 2014 John Wiley & Sons, Ltd.