Age determination of marine sediments in the western North Pacific by as partic acid chronology

The ages of fossil planktonic foraminifera,Pulleniatina obliquiloculata, in sediments (core 3bPC) from the western North Pacific were determined by aspartic acid chronology, which uses the racemization reaction rate constant of aspartic acid (k_Asp). Aspartic acid racemization-based ages (Asp ages) ranged from 7,600 yrBP at the surface, to 307,000 yrBP at a depth of 352.9 cm in the sediments. This sediment core was also dated by the glacial-interglacial fluctuation of δ¹⁸O chronology, and the ages determined by both chronologies were compared. The ages derived from aspartic acid chronology and δ¹⁸O stratigraphy were more or less consistent, but there appeared to be some differences in age estimates between these two dating methods at some depths within the core. In the core top sediments, the likely cause for the age discrepancy could be the loss of the surface sediment during sampling of the core. At depths of 66.3 and 139 cm within the core, Asp ages indicated reduced sedimentation rates duringca. 60,000-80,000 yrBP andca. 140,000–190,000 yrBP. The maximum age differences in both chronologies are 33,000 yr and 46,600 yr during each of these periods. These anomalous reductions in sedimentation rates occurring during these periods could possibly be related to some geological events, such as an increased dissolution effect of the calcium carbonate in the western North Pacific. Another possible reason for these age differences could be the unreliability in δ¹⁸O ages of core 3bPC as they were estimated by δ¹⁸O ages of another core, 3aPC.     

A Box Model of Glacial-Interglacial Variability in the Japan Sea

The Japan Sea has experienced drastic changes in the last 60 ka: the surface water was colder than the present value by five degrees and extremely freshened (24 ppt) in the last glacial maximum (15 ka), and then it contained Oyashio water for a few thousand years. It is an open question whether the inflow-outflow pattern was entirely reversed, opposite to the present exchange with an inflow through Tsushima Strait and an outflow through Tsugaru Strait. A box model is employed with two boxes representing the northern and the southern half domains in the upper (300-m-thick) layer. The model is driven by atmospheric forcing and inflow through Tsushima Strait and/or Tsugaru Strait. Here, the net transport through Tsushima to Tsugaru is given in the model. A baroclinic component is added to the net transport through each strait. It is the baroclinic components that allow the upper and the lower portions to flow to the opposite directions in the straits, and hence a reversal flow becomes possible against the net transport, under the condition of an extremely freshened Japan Sea. The fresh surface layer in 1814 ka is attributable to a near-shutoff of the inflow due to the low sea level. Shortly after the near-shutoff, the baroclinic transport through Tsugaru Strait yields intrusion of the Oyashio water into the Japan Sea. Thus, it is implied that Oyashio water existed in the Japan Sea a few thousand years after the reopening of Tsugaru Strait, even though the net transport was one-way, similar to the present state.     

Growth performance of exotic and indigenous tree species in saline soils in Turkana, Kenya

In the arid zone of central Turkana, north-western Kenya, where soil salinity affects 15–20% of the rangelands, growth performances of trees planted in saline soil rehabilitation trials have not been evaluated. Tree-planting trials have emphasised exotic species over indigenous ones. However, advantages and disadvantages of promoting exotic tree species have not been examined. The current study was aimed at evaluating growth performance of seven exotic and nine indigenous tree species used in saline soil rehabilitation trials. The tree species were established from 6-month-old saplings using microcatchments (FT1) from 1988 through 1990 and pitting treatment (FT2) from 1989 through 1992. The soils in FT1 and FT2 treatments were moderately to highly saline. The exotic tree species produced greater cover and volume during the first year (FT1) but by the second year, production was not sustained due to greater mortality (FT1 & FT2). The indigenous species in general had higher survival rates. Relative growth rates (RGR) of exotic and indigenous species did not differ (FT1 & FT2). Tree mortality was negatively correlated with RGR for exotic species in FT1 but not for indigenous ones. However, changes in plant performance were not in response to salinity alone. Rather, water scarcity superimposed on soil salinity might have influenced plant growth performance. Greater water and salinity stress and subsequently greater mortality in exotic species provided a more convincing reason for promotion of indigenous tree species. In the future, knowledge of salinity distribution and selection of indigenous species to match this will be a better way of rehabilitating sites affected by soil salinity in the arid zone of central Turkana, north-western Kenya.     

A method for quantitative evaluation of carbonate dissolution in deep-sea sediments and its application to paleoceanographic reconstruction

A method is proposed by which the degree of attrition of the tests of certain foraminifera species, such as Globorotalia menardii and Globorotalia tumida, is used to “scale” the amount of CaCO₃ that has been dissolved from sediment. The scale is calibrated experimentally in the laboratory. The method has been applied to three calcareous cores from the Pacific and the Indian Oceans. It is shown that the original CaCO₃ contents in these cores were high (82–95%) and relatively uniform compared to the present down-core values. About 65 to 85% of the originally deposited CaCO₃ has been dissolved, corresponding to dissolution rates on the order of 0.1-0.3 moles/cm²/yr. These results indicate that appreciable solution could have occurred on sea floor rich in calcareous sediments and that the variation in CaCO₃ content in a core may have resulted largely from dissolution. The difference in the degree of solution between glacial and interglacial sediments in these cores is not so distinct, with ? 10% less intense dissolution during glacial times on the average. However, the dissolution minimum occurring around the late Wisconsin glaciation (10,000–20,000 yr B.P.) previously noted in several cores elsewhere is confirmed. At that time, near the site of core M70 PC-20 in the southwest Pacific, the $\text{CO}{}_3{}^{\mathrm{2?}}$ concentration of the bottom water is estimated to have been approximately 5% higher than the present value, and the calcite lysocline was about 300 m deeper. To evaluate possible variations in CaCO₃ deposition rate across the glacial-interglacial transitions requires precise age control, which the present study lacks.     

Variations in trace elements,isotopes, and organic geochemistry during the Hangenberg Crisis,Devonian–Carboniferous transition,northeastern Vietnam

The Hangenberg Crisis at the Devonian–Carboniferous boundary is known as a polyphase extinction event that affected more than 45 % of marine and terrestrial genera. As the cause of this event is still debated, analyses were carried out on sedimentary samples from the Devonian–Carboniferous Pho Han Formation in northeastern Vietnam to reconstruct the paleoenvironment around the time of this event using stable carbon isotopes; total sulfur; manganese; vanadium; molybdenum; and sedimentary organic matter, such as dibenzothiophenes, cadalene, and regular steranes. These geochemical signatures provide a high‐resolution redox history for this section and show that transgression‐driven high primary productivity, possibly enhanced by terrestrial input, caused severe oxygen depletion along the continental margin of the South China block during the Hangenberg Crisis.     

Production of the Blood Pressure Lowing Peptides from Brown Alga （ Undaria pinnatifida ）

Brown alga （ Undaria pinnatifida） was treated with alginate lyase and hydrolyzed using 17 kinds of proteases and the inhibitory activity of the hydrolysates for the angiotensin-I-converting enzyme （ACE） was measured. Four hydrolysates with potent ACE-inhibitory activity were administered singly and orally to spontaneously hypertensive rats （SHRs）. The systolic blood pressure of SHRs decreases significantly after single oral administration of the brown alga hydrolysates by pro- tease S ＇ Amano＇ （from Bacillus stearothermophilus） at the concentration of 10 （mg protein） （kg body weight）^ - 1. In the 17 weeks of feeding experiment, 7-week-old SHRs were fed standard diet supplemented with the brown alga hydrolysates for 10 weeks. In SHRs fed 1.0 and 0.1% brown alga hydrolysates, elevating of systolic bloodpressure was significantly suppressed for 7 weeks. To elucidate the active components, the brown alga hydrolysates were fractionated by 1-butanol extraction and HPLC on a reverse-phase column. Seven kinds of ACE-inhibitory peptides were isolated and identified by amino acid composition analysis, sequence analysis, and LC-MS with the results Val-Tyr, Ile-Tyr, Ala-Trp, Phe-Tyr, Val-Trp, Ile-Trp, and Leu-Trp. Each peptide was determined to have an antihypertensive effect after a single oral administration in SHRs. The brown alga hydrolysates were also confirmed to decrease the blood pressure in humans.     

Hydrogen isotopic substitution of solid methylamine through atomic surface reactions at low temperatures: A potential contribution to the D/H ratio of methylamine in molecular clouds

We experimentally studied hydrogen (H)–deuterium (D) substitution reactions of solid methylamine (CH₃NH₂) under astrophysically relevant conditions. We also calculated the potential energy surface for the H–D substitution reactions of methylamine isotopologues using quantum chemical methods. Despite the relatively large energy barrier of more than 18 kJ mol^?1, CH₃NH₂ reacted with D atoms to yield deuterated methylamines at 10 K, suggesting that the H–D substitution reaction proceeds through quantum tunneling. Deuterated methylamines reacted with H atoms as well. On the basis of present results, we propose that methylamine has potential for D enrichment through atomic surface reactions on interstellar grains at very low temperatures in molecular clouds. D enrichment would occur in particular in the methyl group of methylamine.     

Descriptive and Predictive Growth Curves in Energy System Analysis

This study reviews a variety of growth curve models and the theoretical frameworks that lay behind them. In many systems, growth patterns are, or must, ultimately be subjected to some form of limitation. A number of curve models have been developed to describe and predict such behaviours. Symmetric growth curves have frequently been used for forecasting fossil fuel production, but others have expressed a need for more flexible and asymmetric models. A number of examples show differences and applications of various growth curve models. It is concluded that these growth curve models can be utilised as forecasting tools, but they do not necessarily provide better predictions than any other method. Consequently, growth curve models and other forecasting methods should be used together to provide a triangulated forecast. Furthermore, the growth curve methodology offers a simple tool for resource management to determine what might happen to future production if resource availability poses a problem. In the light of peak oil and the awareness of natural resources being considered as a basis for the continued well-being of the society and the mankind, resource management should be treated as an important factor in future social planning.     

An assessment of conditions before and after the 1998 Tam Pokhari outburst in the Nepal Himalaya and an evaluation of the future outburst hazard

On 3 September 1998, a glacial lake outburst flood (GLOF) that originated from Tam Pokhari occurred in the Hinku valley of the eastern Nepal Himalaya. This study analyses the lake's geomorphic and hydrologic conditions prior to the outburst, and evaluates the conditions that could contribute to a future flood through photogrammetric techniques. We processed high‐resolution Corona KH‐4A (2.7 m) and ALOS PRISM (2.5 m) stereo‐images taken before and after the GLOF event, and produced detailed topographic maps (2‐m contour interval) and DEMs (5 m × 5 m). We (re‐) constructed lake water surfaces before (4410 ± 5 m) and after (4356 ± 5 m) the outburst, and reliably estimated the lake water surface lowering (54 ± 5 m) and the water volume released (19.5 ± 2.2 × 10⁶ m³) from the lake, showing good agreement with the results obtained from ground‐based measurements. The most relevant conditions that may have influenced the catastrophic drainage of Tam Pokhari in 1998 include the presence of: (i) a narrow (75 ± 6 m), steep (up to 50°) and high (120 ± 5 m) moraine dam; (ii) high lake level (8 ± 5 m of freeboard) and (iii) a steep overhanging glacier (>40°). The lake outburst substantially altered the immediate area, creating a low and wide (>500 m) outwash plain below the lake, a wide lake outlet channel (~50 m) and a gentle channel slope (~3–5°). Our new data suggest that the likelihood of a future lake outburst is low. Our results demonstrate that the datasets produced by photogrammetric techniques provide an excellent representation of micro‐landform features on moraine dams, lake water surfaces and the changes in both over time, thereby allowing highly accurate pre‐ and post‐GLOF (volumetric) change analysis of glacial lakes. Furthermore, it enables precise measurement of several predictive variables of GLOFs that can be useful for identifying potentially dangerous glacial lakes or prioritizing them for detailed field investigations. Copyright © 2015 John Wiley & Sons, Ltd.