Particle size distributions in the upper 100 m water column and their implications for animal feeding in the plankton     

George A. Jackson  David M. Checkley Jr 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(3):283-297

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Urban China in transformation: Hybrid economy,juxtaposed space,and new testing ground for geographical enquiries     

George C S LIN 《中国地理科学(英文版)》2011,21(1):1-16

History has brought us into a significant moment when the majority of the human kind has taken up resi-dence in urban settlements. The focus of global urbanization has shifted to the developing world and the center of manufacturing is no longer confined to the Global North. This paper provides a periodical assessment of the current status of China’s urban transformation in the global context of a shifting emphasis of industrialization and urbaniza-tion. China’s phenomenal urban transformation deserves a special attention not only because of its unparalleled scale and speed but also because of its distinct trajectory of growth that does not conform to normal theoretical ex-pectations. The results of assessment revealed an urban economy with remarkable hybridity, a society that is in-creasingly stratified, polarized, and segregated, and a juxtaposed urban space undergoing restless and pervasive transformation. A decentering world should entail a decentering knowledge production. A critical reflection upon the Chinese patterns and processes of urban transformation has identified 4 main issues with great potentials for inno-vative knowledge production, namely: 1) privatization and economic development; 2) state, society, and space; 3) urbanization of capital, labor, and land; and 4) the environment and Chinese political ecology. The paper closes with the remark that a rapidly transforming urban China has presented itself as a fertile and resourceful testing ground for critical and innovative geographic enquiries.  相似文献   

The influence of light on nitrogen cycling and the primary nitrite maximum in a seasonally stratified sea     

Katherine R.M. Mackey  Laura Bristow  David R. Parks  Mark A. Altabet  Anton F. Post  Adina Paytan 《Progress in Oceanography》2011,91(4):545-560

In the seasonally stratified Gulf of Aqaba Red Sea, both release by phytoplankton and oxidation by nitrifying microbes contributed to the formation of a primary nitrite maximum (PNM) over different seasons and depths in the water column. In the winter and during the days immediately following spring stratification, formation was strongly correlated (R² = 0.99) with decreasing irradiance and chlorophyll, suggesting that incomplete reduction by light limited phytoplankton was a major source of . However, as stratification progressed, continued to be generated below the euphotic depth by microbial oxidation, likely due to differential photoinhibition of and oxidizing populations. Natural abundance stable nitrogen isotope analyses revealed a decoupling of the δ¹⁵N and δ¹⁸O in the combined and pool, suggesting that assimilation and nitrification were co-occurring in surface waters. As stratification progressed, the δ¹⁵N of particulate N below the euphotic depth increased from −5‰ to up to +20‰.N uptake rates were also influenced by light; based on ¹⁵N tracer experiments, assimilation of , , and urea was more rapid in the light (434 ± 24, 94 ± 17, and 1194 ± 48 nmol N L⁻¹ day⁻¹ respectively) than in the dark (58 ± 14, 29 ± 14, and 476 ± 31 nmol N L⁻¹ day⁻¹ respectively). Dark assimilation was 314 ± 31 nmol N L⁻¹ day⁻¹, while light assimilation was much faster, resulting in complete consumption of the ¹⁵N spike in less than 7 h from spike addition. The overall rate of coupled urea mineralization and oxidation (14.1 ± 7.6 nmol N L⁻¹ day⁻¹) was similar to that of oxidation alone (16.4 ± 8.1 nmol N L⁻¹ day⁻¹), suggesting that mineralization of labile dissolved organic N compounds like urea was not a rate limiting step for nitrification. Our results suggest that assimilation and nitrification compete for and that N transformation rates throughout the water column are influenced by light over diel and seasonal cycles, allowing phytoplankton and nitrifying microbes to contribute jointly to PNM formation. We identify important factors that influence the N cycle throughout the year, including light intensity, substrate availability, and microbial community structure. These processes could be relevant to other regions worldwide where seasonal variability in mixing depth and stratification influence the contributions of phytoplankton and non-photosynthetic microbes to the N cycle.  相似文献   

The insoluble carbonaceous material of CM chondrites: A possible source of discrete organic compounds under hydrothermal conditions     

Hikaru YABUTA  Lynda B. WILLIAMS  George D. CODY  Conel M. O'D. ALEXANDER  Sandra PIZZARELLO 《Meteoritics & planetary science》2007,42(1):37-48

Abstract— We report on the molecular analyses of the water‐ and solvent‐soluble organic compounds released from the insoluble organic material (IOM) of the Murray meteorite upon treatment with weight‐equivalent amounts of water and under conditions of elevated temperature and pressure. A varied suite of compounds was identified by gas chromatography‐mass spectrometry (GC‐MS). C₃‐C₁₇ alkyl dicarboxylic acids and N‐ and O‐containing hydroaromatic and aromatic compounds were found in the water extracts. The solvent extracts contained N‐, O‐, and S‐containing aromatic compounds, a large number of their isomers and homologs, and a series of polycyclic aromatic hydrocarbons (PAHs) of up to five rings, together with noncondensed aromatic species such as substituted benzenes, biphenyl, and terphenyls as well as their substituted homologs, and hydrated PAHs. Isotopic analyses showed that residue IOMs after hydrothermal treatment had lower deuterium and ¹⁵N content than the untreated material (ΔD = ?833‰ and Δ¹⁵N = ?24.1) but did not differ from it in ¹³C composition. The effect of the hydrothermolytic release was recorded in significant differences between the NMR spectra of untreated and residue IOM. A possible relation to common precursors for the dicarboxylic acids found in the IOM and bulk extracts is discussed.  相似文献   

Preface     

George H. Denton 《Geografiska Annaler: Series A, Physical Geography》1999,81(2):105-106

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Climatic change in Central Asia during MIS 3/2: a case study using biological responses from Lake Baikal   总被引：5，自引：0，他引：5  

George E.A. Swann  Anson W. Mackay  Melanie J. Leng  Francois Demory 《Global and Planetary Change》2005,46(1-4):235

A Marine Isotope Stage (MIS) 3/early MIS 2 section from a structural high along the east coast of the North Basin of Lake Baikal was analysed for diatoms, C/N ratios, and organic carbon isotope ratios. Diatoms were present throughout MIS 3 and early MIS 2, with high concentrations of the planktonic taxa Cyclotella sp. c.f. gracilis between 54 and 51.5 kyr BP indicating relatively warm, interstadial, conditions. Following a %TOC inferred climatic cooling between 43.2 and 39.1 kyr BP, evidence of a more muted δ¹³C_(organic) and %TOC inferred climatic warming from c. 39.1–34.7 kyr BP coincides with a period of very high diatom concentrations, indicating high aquatic productivity, at the Buguldeika Saddle in the South Basin of Lake Baikal. No evidence exists for a ‘Kuzmin’ catchment erosional event in the North Basin during MIS 3. This, however, may reflect the location of the coring site away from major riverine inputs. Abrupt climatic cooling at the culmination of both warm phases in the North Basin are associated, on the basis of the palaeomagnetic age-model and correlations to existing sites in Lake Baikal, with the initiation of Heinrich events 5 (c. 50 kyr BP) and 4 (c. 35 kyr BP), respectively, in the North Atlantic. The amount of organic material declines across the MIS 3/MIS 2 transition while constant C/N ratios suggest organic material to be predominantly derived from phytoplankton. An increase in δ¹³C_(organic) at the MIS 3/MIS 2 transition may therefore indicate changes in aquatic productivity, pCO₂ or the inorganic carbon pool.  相似文献   

Mid-infrared (5–100 μm) reflectance spectra and optical constants of ten phyllosilicate minerals     

Timothy D. Glotch  George R. Rossman  Oded Aharonson 《Icarus》2007,192(2):605-622

We have derived the real and imaginary indices of refraction for 10 phyllosilicate minerals—montmorillonite, beidellite, nontronite, hectorite, saponite, illite, illite–smectite (60/40 interlayered) kaolinite, halloysite, and serpentine—from 100–2000 cm⁻¹ (5–100 μm) at 2 cm⁻¹ spectral sampling using classical Lorentz–Lorenz dispersion theory. We present the real and imaginary indices and the oscillator parameters with which they were modeled. Use of these optical constants will aid in the modeling of thermal infrared spectra of planets, asteroids, interplanetary and interstellar dust, and protoplanetary disks around nearby stars.  相似文献   

Suspended sediment transport from the Gironde estuary (France) onto the adjacent continental shelf     

George P. Allen  Patrice Castaing 《Marine Geology》1973,14(5):47-53

Current velocity and suspended sediment concentration measurements at anchor stations in the downstream extremity of the Gironde estuary indicate that during periods of high river discharge, a significant amount of suspended sediment is transported out of the estuary onto the adjacent continental shelf. The vertical profile of the residual (non-tidal) suspended sediment flux is similar to that of the residual current velocity, with a net upstream flux near the bottom and an overlying seaward-directed transport. The overall, depth-integrated result is a net seaward transport of suspended sediment out of the estuary. It appears that this net seaward transport varies directly with tidal amplitude.Aerial photography and water sampling indicate that during high river inflow, the downstream extremity of the turbidity maximum extends onto the continental shelf at ebb tide. The tidal and coastal current patterns of the inlet and inner shelf induce a northward transport of the turbid estuarine water, and at each tidal cycle, a certain amount of suspended sediment leaves the estuary; part of this sediment is deposited in a silt and clay zone on the continental shelf.  相似文献   

The dipole anisotropy of the 2 Micron All-Sky Redshift Survey     

P. Erdo&#;du  J. P. Huchra  O. Lahav  M. Colless  R. M. Cutri  E. Falco  T. George  T. Jarrett  D. H. Jones  C. S. Kochanek  L. Macri  J. Mader  N. Martimbeau  M. Pahre  Q. Parker  A. Rassat  W. Saunders 《Monthly notices of the Royal Astronomical Society》2006,368(4):1515-1526

We estimate the acceleration on the Local Group (LG) from the 2 Micron All-Sky Redshift Survey (2MRS). The sample used includes about 23 200 galaxies with extinction-corrected magnitudes brighter than   K _s= 11.25  and it allows us to calculate the flux-weighted dipole. The near-infrared flux-weighted dipoles are very robust because they closely approximate a mass-weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the cosmic microwave background (CMB) dipole drops to  12°± 7°  at around  50  h ⁻¹ Mpc  , but then increases at larger distances, reaching  21°± 8°  at around  130  h ⁻¹ Mpc  . Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to  14°± 7°  away from the CMB velocity dipole. In both cases, the dipole seemingly converges by  60  h ⁻¹ Mpc  . Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters  Ω^0.6_m/ b _L= 0.40 ± 0.09  .  相似文献   

From the editors     

Xiaozhai Qi George C. Lee 《地震工程与工程振动(英文版)》2005,4(2):I0002-I0002

As the Journal of Earthquake Engineering and Engineering Vibration enters its fourth year of publication, we believe the first six issues are on the right track toward promoting scientific exchange between China, the United States and the international community. Our contributors have hailed from many countries throughout the world including Canada, China, Greece, Italy, India, Japan, Korea, New Zealand, Turkey and the United States.  相似文献