The effects of possible contamination by sample holders on samples to be returned by Hayabusa2     

Naoki Shirai  Yuzuru Karouji  Kazuya Kumagai  Masayuki Uesugi  Kaori Hirahara  Motoo Ito  Naotaka Tomioka  Kentaro Uesugi  Akira Yamaguchi  Naoya Imae  Takuji Ohigashi  Toru Yada  Masanao Abe 《Meteoritics & planetary science》2020,55(7):1665-1680

Chemical compositions of materials used for new sample holders (vertically aligned carbon nanotubes [VACNTs] and polyimide film), which were developed for the analysis of Hayabusa2‐return samples, were determined by instrumental neutron activation analysis and/or instrumental photon activation analysis, to estimate contamination effects from the sample holders. The synthetic quartz plate used for the sample holders was also analyzed. Ten elements (Na, Al, Cr, Mn, Fe, Ni, Eu, W, Au, and Th) and 14 elements (Na, Al, K, Sc, Ti, Cr, Zn, Ga, Br, Sb, La, Eu, Ir, and Au) could be detected in the VACNTs and polyimide film, respectively. The VACNT data show that contamination by this material with respect to the Murchison meteorite is negligible in terms of the elemental ratios (e.g., Fe/Mn, Na/Al, and Mn/Cr) used for the classification of meteorites due to the extremely low density of VACNTs. However, for the Au/Cr ratio, even small degrees (1.7 wt%) of contamination by VACNTs will change the Au/Cr ratio. Elemental ratios used for the classification of meteorites are only influenced by large amounts of contamination (>60 wt%) of polyimide film, which is unlikely to occur. In contrast, detectable effects on Ti isotopic compositions are caused by >0.1 and >0.3 wt% contamination by VACNTs and polyimide film, respectively, and Hf isotopic changes are caused by >0.1 wt% contamination by VACNTs. The new sample holders (VACNTs and polyimide film) are suitable for chemical classification of Hayabusa2‐return samples, because of their ease of use, applicability to multiple analytical instruments, and low contamination levels for most elements.  相似文献   

Peaks of People: Using Topographic Prominence as a Method for Determining the Ranked Significance of Population Centers     

Garrett Dash Nelson  Ryan McKeon 《The Professional geographer》2019,71(2):342-354

This article borrows a statistical method from physical geography—topographical prominence—to suggest a new technique for measuring the relative significance or rank of population centers. Unlike raw population measures, prominence gives consideration to both the spatial intensity of concentrated population areas as well as the spatial dependence or independence of neighboring settlement clusters in relation to one another. We explain how to apply the topographic prominence calculation method to gridded population data and examine its practical utility through case studies of several U.S. states. We then discuss some ways in which parametric choices about point-to-surface transformations can result in considerably different outcomes and offer further suggestions for conceptualizing and measuring population center significance.  相似文献   

Helical jet in the gravitationally lensed blazar PKS1830-211     

S. Nair  C. Jin  M. A. Garrett 《Monthly notices of the Royal Astronomical Society》2005,362(4):1157-1166

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Rethinking the Land: An Exhibition of Ulster Maps     

Garrett Carr 《The Cartographic journal》2017,54(2):173-180

The author curates a touring exhibition of Northern Ireland cartography, called Mapping Alternative Ulster. The project emerged from a dissatisfaction with how Northern Ireland is represented in maps, and one example is given. To counter them, he sought independent cartographers making original maps. The curator discusses the criteria he applied when selecting work for the show. He wanted maps with politics, although not the region’s traditional sectarian politics. All the selected maps constitute arguments, critiquing problems in the lived environment or drawing attention to valuable things that may be at risk. The latter sections of the article discuss five of the contributors and looks at their work in detail. In the conclusion, the impact of the exhibition is assessed by examining visitor comments. The paper is illustrated.  相似文献   

Solar radiation management and ecosystem functional responses     

Akihiko Ito 《Climatic change》2017,142(1-2):53-66

Geoengineering such as solar radiation management (SRM) can be an emergent option to avoid devastating climatic warming, but its ramifications are barely understood. The perturbation of the Earth’s energy balance, atmospheric dynamics, and hydrological cycling may exert unexpected influences on natural and human systems. In this study, I evaluate the impacts of SRM deployment on terrestrial ecosystem functions using a process-based ecosystem model (the Vegetation Integrative Simulator for Trace gases, VISIT) driven by the climate projections by multiple climate models. In the SRM-oriented climate projections, massive injection of sulphate aerosols into the stratosphere lead to increased scattering of solar radiation and delayed anthropogenic climate warming. The VISIT simulations show that canopy light absorption and gross primary production are enhanced in subtropics in spite of the slight decrease of total incident solar radiation. The retarded temperature rise during the deployment period leads to lower respiration, and consequently, an additional net terrestrial ecosystem carbon uptake by about 20%. After the SRM termination, however, along with the temperature rise, this carbon is released rapidly to the atmosphere. As a result of altered precipitation and radiation budget, simulated runoff discharge is suppressed mainly in the tropics. These SRM-induced influences on terrestrial ecosystems occurr heterogeneously over the land surface and differed among the ecosystem functions. These responses of terrestrial functions should be taken into account when discussing the costs and benefits of geoengineering.  相似文献   

Thermodynamic properties of MgSiO3 ilmenite from vibrational spectra     

Anne M. Hofmeister  Eiji Ito 《Physics and Chemistry of Minerals》1992,18(7):423-432

Unpolarized infrared (IR) reflectance spectra for MgSiO₃ ilmenite taken from a single-crystal and from a densly packed polycrystalline sample possessed all eight peaks mandated by symmetry between 337 and 850 cm^?1. Polarizations were inferred from intensity differences between the two samples. IR peak positions differ by up to 250 cm^?1 from recent calculations, but on average are within 11%. Heat capacity C _p calculated from these data by using a Kieffer-type model are within the experimental uncertainty of calorimetric measurements from 170 to 700 K. Outside this range, calculated C _p is probably accurate within a few percent, based on recent results for garnets. Calculated entropy is only slightly less accurate, giving S ⁰ (298.15 K) as 54.1 ±0.5 J/ mol-K, which is 10% lower than recent estimates based on phase equilibria. The slope of the phase boundary between ilmenite and perovskite is used to predict S ⁰ (298.15 K) of perovskite as 58.7 ±1.4 J/mol-K, which is 10% lower than previous values.  相似文献   

Coupled analysis of floating production systems     

D.L. Garrett   《Ocean Engineering》2005,32(7):802-816

Fully coupled global analysis of Floating Production Systems, including the vessel, the mooring system and the riser system is described. Design of the system can be a daunting task, involving more than 1000 load cases for global analysis. The primary driver for the mooring system and for the riser system is motion of the vessel. Vessel motions are driven by environmental forces, but are restrained by forces from the mooring and riser systems. Numerical models and procedures that provide accurate and efficient global modeling of the Floating Production System are presented. Both Time Domain and Frequency Domain procedures are included. The accuracy and efficiency of the procedures are illustrated in an example: a large semi with 16 mooring lines and 20 risers. The procedures provide the accuracy and efficiency for use of fully coupled analysis in design of Floating Production Systems from concept selection to final design, installation and operation.  相似文献   

Standing Crops of Planktonic Ciliates and Copepod Nauplii in the Subarctic North Pacific and the Bering Sea in Summer     

Hiroshi Ito  Akira Taniguchi 《Journal of Oceanography》2001,57(3):333-339

Abundances and biomasses of planktonic ciliates and copepod nauplii, major components of the microzooplankton community, were investigated in the subarctic North Pacific and the Bering Sea in summer of 1997. Their regional variation was illustrated by demarcating the entire area into five regions. Ciliates always predominated both in abundance (>94%) and biomass (>78%) over nauplii. Regional means of ciliates in the water column were higher in the Alaskan Gyre (120 × 10⁶ cells/m²) and the Western Subarctic Gyre (110 × 10⁶ cells/m²) in terms of abundance, and rich in the Bering Sea Gyre (360 mgC/m²) and the Western Subarctic Gyre (340 mgC/m²) in terms of biomass. By contrast, standing crops of ciliates were poor in the Oyashio Region (67 × 10⁶ cells/m²; 170 mgC/m²) and the Transition Region (64 × 10⁶ cells/m²; 160 mgC/m²). The values of biomass reported here are generally in agreement with the values reported previously from the Bering Sea Gyre and the Alaskan Gyre but are considerably higher than the previous value found in the Western Subarctic Gyre. No significant correlations could be found between chlorophyll a crop and standing crops of ciliates and copepod nauplii over the entire subarctic North Pacific and the Bering Sea during this summer.  相似文献   

The effects on water mass formation of surface mixed layer timedependence and entrainment fluxes     

Chris Garrett  Amit Tandon 《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12):1991-2006

An air-sea buoyancy flux out of the ocean between the surface outcroppings of different isopycnals must be balanced by a convergence of advective and diffusive fluxes of buoyancy across those isopycnals (Walin, 1982; Tziperman, 1986; Garrett et al., 1995). For steady conditions, the diapycnal diffusive flux due to vertical mixing in the surface mixed layer is very small, so that the advective buoyancy flux dominates (Speer, 1993; Garrett et al., 1995). The associated advective buoyancy flux can then be used to estimate the volume flux of water out of the base of the surface mixed layer. The resulting thermodynamic algorithm provides a valuable estimate of water mass formation in the ocean.In contrast, for the time-dependent real ocean with horizontal and vertical gradients of the horizontal buoyancy gradient, diurnal and seasonal mixed layer deepening and entrainment in the presence of a buoyancy jump at the base of the mixed layer contributes to the annual volume flux out of the base of the deepest (wintertime) mixed layer. The mismatch between the predictions of the ideal algorithm and measured rates of water mass formation (Speer, 1997) may thus be partly due to mixed layer processes rather than diapycnal mixing in the thermocline.  相似文献   

Response of plant growth to surface water balance during a summer dry period in the Kazakhstan steppe     

Yoshihiro Iijima  Tsuneo Kawaragi  Takehiko Ito  Kanat Akshalov  Atsushi Tsunekawa  Masato Shinoda 《水文研究》2008,22(16):2974-2981

In drylands, water deficit is the primary factor limiting plant growth. In the present study, surface energy balance and plant growth (above‐ground and below‐ground biomass) were measured continuously during the 2002 growing season in semiarid grassland in the northern part of Kazakhstan, Central Asia. Although there was above normal total rainfall during the 2002 growing season (May–November; 244 mm over 183 days), there was a dry period during July and August. Evaporative water was effectively supplied by precipitation and surface soil moisture during the wet season (May and June), during which time above‐ground biomass increased. During the early stages of the dry period, mature plants were likely to tap deeper sources of soil moisture, representing stored snowmelt water. As the soil moisture content decreased during the summer dry period due to the high levels of evapotranspiration and lack of precipitation, the evaporative fraction and above‐ground biomass rapidly decreased, whereas the below‐ground biomass increased. These results suggest that in summer, soil moisture acts to store water, and that soil moisture is essential for plant growth as a direct source of water during the dry period in natural grasslands in the Kazakhstan steppe. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献