The effect of glucose on the productivity of seawater: An experimental approach using controlled aquatic ecosystems

Small quantities (1 to 5 mg litre) of glucose were added to 60-ton enclosed water columns together with inorganic nutrients. Heterotrophic production by bacteria in the glucose-enriched water columns depressed photosynthetic production by algae. This effect was believed to have been caused by heterotrophic growth out-competing the autotrophic organisms for a limited supply of nitrate. Secondary and tertiary production in the glucose-enriched water columns was higher than under conditions of predominantly autotrophic production.     

Heat flow and quantity of methane deduced from a gas hydrate field in the vicinity of the Dnieper Canyon,northwestern Black Sea

Seismic reflection data document for the first time the existence of a BSR in a limited area west of the Dnieper Canyon in the northwestern Black Sea. Seismic wide-angle data suggest that gas hydrates occupy in average 15±2% of the pore space in a zone of 100 m in thickness. A conservative quantification of the amount of methane associated with this gas hydrate occurrence is about 12±3×10¹¹ m³ (0.6±0.2 Gt of methane carbon). Conductive heat flow deduced from the BSR depth is in the range of 21±6 to 55±15 mW m^–2.     

Crack Coalescence in Molded Gypsum and Carrara Marble: Part 1. Macroscopic Observations and Interpretation

Cracking and coalescence behavior has been studied experimentally with prismatic laboratory-molded gypsum and Carrara marble specimens containing two parallel pre-existing open flaws. This was done at both the macroscopic and the microscopic scales, and the results are presented in two separate papers. This paper (the first of two) summarizes the macroscopic experimental results and investigates the influence of the different flaw geometries and material, on the cracking processes. In the companion paper (also in this issue), most of the macroscopic deformation and cracking processes shown in this present paper will be related to the underlying microscopic changes. In the present study, a high speed video system was used, which allowed us to precisely observe the cracking mechanisms. Nine crack coalescence categories with different crack types and trajectories were identified. The flaw inclination angle (β), the ligament length (L), that is, intact rock length between the flaws, and the bridging angle (α), that is, the inclination of a line linking up the inner flaw tips, between two flaws, had different effects on the coalescence patterns. One of the pronounced differences observed between marble and gypsum during the compression loading test was the development of macroscopic white patches prior to the initiation of macroscopic cracks in marble, but not in gypsum. Comparing the cracking and coalescence behaviors in the two tested materials, tensile cracking generally occurred more often in marble than in gypsum for the same flaw pair geometries.

Late Carboniferous foreland basin formation and Early Carboniferous stretching in Northwestern Europe: inferences from quantitative subsidence analyses in the Netherlands

The large thickness of Upper Carboniferous strata found in the Netherlands suggests that the area was subject to long-term subsidence. However, the mechanisms responsible for subsidence are not quantified and are poorly known. In the area north of the London Brabant Massif, onshore United Kingdom, subsidence during the Namurian–Westphalian B has been explained by Dinantian rifting, followed by thermal subsidence. In contrast, south and east of the Netherlands, along the southern margin of the Northwest European Carboniferous Basin, flexural subsidence caused the development of a foreland basin. It has been proposed that foreland flexure due to Variscan orogenic loading was also responsible for Late Carboniferous subsidence in the Netherlands. In the first part of this paper, we present a series of modelling results in which the geometry and location of the Variscan foreland basin was calculated on the basis of kinematic reconstructions of the Variscan thrust system. Although several uncertainties exist, it is concluded that most subsidence calculated from well data in the Netherlands cannot be explained by flexural subsidence alone. Therefore, we investigated whether a Dinantian rifting event could adequately explain the observed subsidence by inverse modelling. The results show that if only a Dinantian rifting event is assumed, such as is found in the United Kingdom, a very high palaeowater depth at the end of the Dinantian is required to accommodate the Namurian–Westphalian B sedimentary sequence. To better explain the observed subsidence curves, we propose (1) an additional stretching event during the Namurian and (2) a model incorporating an extra dynamic component, which might well explain the very high wavelength of the observed subsidence compared with the wavelength of the predicted flexural foreland basin.     

Multi-factors on biodegradation kinetics of polycyclic aromatic hydrocarbons (PAHs) by Sphingomonas sp. a bacterial strain isolated from mangrove sediment

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediment is an attractive remediation technique and its success depends on biodegradation kinetics, and the optimal condition for the PAH-degrading isolates; however, information on this aspect is still scarce. The effects of multi-factors on biodegradation of phenanthrene, a 3-ring model PAH, in contaminated sediment slurry by Sphingomonas sp. a bacterial strain isolated from surface mangrove sediment, were investigated using the orthogonal experimental design (form L(16)(4(5))). The most significant factors were salinity and inoculum size, while the effects of phenanthrene concentrations, nutrient addition and temperatures were insignificant. The optimal biodegradation condition in contaminated mangrove sediment slurry was 30 degrees C, 15 ppt salinity, a carbon/nitrogen ratio of 100:1 (the background ratio in sediment) and an inoculum size of 10(6) most probable number g(-1) sediment. The phenanthrene biodegradation could be best described by the first order rate model, C=C(0)e(-kt), where k (the rate constant) is equaled to 0.1185, under the optimal condition. The kinetic model was verified and its validity in predicting biodegradation by Sphingomonas sp. at various phenanthrene concentrations was proved by experimental data.     

Field observations on correlation of fatty acid profiles between suspended particulate matter and green-lipped mussels in subtropical waters of Hong Kong

By analysis of the fatty acid profiles in mussel tissues and suspended particulate matter (SPM) in water, the present study showed a significant relationship of the trophic linkage between mussels and the SPM. At seven locations from inner to outer areas along the eutrophic Tolo Harbour and Tolo Channel, Hong Kong, the composition (as percentage of total fatty acids) of both monoenoic and polyunsaturated fatty acids in the tissues of green-lipped mussels Perna viridis and SPM in water had significant correlation (p<0.01). In particular, the composition of docosahexaenoic acid (DHA, 22:6n3) (as percentage of total fatty acids) in mussel tissues was statistically correlated with that in SPM (p<0.01), implying that mussels incorporate DHA, the biomarker of dinoflagellates. Principal component analysis further demonstrated that the fatty acid profiles of SPM were different among locations in the harbour, mid and outer channel of the study area, so were the mussel tissue fatty acid profiles. Cluster analysis of phytoplankton data also revealed the dominance of diatoms in the inner harbour and channel areas, whereas dinoflagellates were abundant in the outer channel waters. The possible implications of using benthic suspension feeders such as green-lipped mussels P. viridis for controlling phytoplankton abundance in coastal waters are discussed.     

Multi-factors on biodegradation kinetics of polycyclic aromatic hydrocarbons (PAHs) by Sphingomonas sp. a bacterial strain isolated from mangrove sediment

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediment is an attractive remediation technique and its success depends on biodegradation kinetics, and the optimal condition for the PAH-degrading isolates; however, information on this aspect is still scarce. The effects of multi-factors on biodegradation of phenanthrene, a 3-ring model PAH, in contaminated sediment slurry by Sphingomonas sp. a bacterial strain isolated from surface mangrove sediment, were investigated using the orthogonal experimental design (form L₁₆(4⁵)). The most significant factors were salinity and inoculum size, while the effects of phenanthrene concentrations, nutrient addition and temperatures were insignificant. The optimal biodegradation condition in contaminated mangrove sediment slurry was 30 °C, 15 ppt salinity, a carbon/nitrogen ratio of 100:1 (the background ratio in sediment) and an inoculum size of 10⁶ most probable number g⁻¹ sediment. The phenanthrene biodegradation could be best described by the first order rate model, C = C₀e^−kt, where k (the rate constant) is equaled to 0.1185, under the optimal condition. The kinetic model was verified and its validity in predicting biodegradation by Sphingomonas sp. at various phenanthrene concentrations was proved by experimental data.     

Experimental investigation of three-dimensional propagation process from surface fault

Experimental study of the formation and propagation of three-dimensional (3D) faults is of great sig- nificance in the understanding of the propagation process developing from initial natural faults. In the study described in this paper, experimental investigations of 3D propagation processes of a type of surface fault are carried out under biaxial compression. The strain field near the surface fault is dy- namically measured and fully analyzed with a high-density Multi-Channel Digital Strain Gauge (MCDSG) and Digital Speckle Correlation Method (DSCM) based on the white-light image analysis. Simultane- ously the micro-fracture process involved in fault formation is observed by a 3D acoustic emission (AE) location system with a set of multi-channel whole-wave record equipment. The experimental results show that the 3D propagation process of surface fault differs greatly from that of the two-dimensional (2D) state and that a new more complicated type of 3D morphological characters and deformation mechanisms are produced. The 3D propagation process of surface faults may be divided into three stages: 1) the first stage of crack propagation initiated by wing cracks; 2) the conversion stage propa- gated by petal cracks; and 3) the second stage of crack propagation formed by shell-shaped fracture surface. The primary propagation patterns of the three stages are different. The corresponding defor- mation fields and micro-fracture distributions are likewise different. The fracture activities from petal cracks especially are of vital importance during surface fault propagation. This is also a key conversion state and marks an intrinsic difference between 2D-like and the 3D state in fault development.     

The Advanced Regional Prediction System (ARPS) – A multi-scale nonhydrostatic atmospheric simulation and prediction model. Part I: Model dynamics and verification

Summary  A completely new nonhydrostatic model system known as the Advanced Regional Prediction System (ARPS) has been developed in recent years at the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma. The ARPS is designed from the beginning to serve as an effective tool for basic and applied research and as a system suitable for explicit prediction of convective storms as well as weather systems at other scales. The ARPS includes its own data ingest, quality control and objective analysis packages, a data assimilation system which includes single-Doppler velocity and thermodynamic retrieval algorithms, the forward prediction component, and a self-contained post-processing, diagnostic and verification package. The forward prediction component of the ARPS is a three-dimensional, nonhydrostatic compressible model formulated in generalized terrain-following coordinates. Minimum approximations are made to the original governing equations. The split-explicit scheme is used to integrate the sound-wave containing equations, which allows the horizontal domain-decomposition strategy to be efficiently implemented for distributed-memory massively parallel computers. The model performs equally well on conventional shared-memory scalar and vector processors. The model employs advanced numerical techniques, including monotonic advection schemes for scalar transport and variance-conserving fourth-order advection for other variables. The model also includes state-of-the-art physics parameterization schemes that are important for explicit prediction of convective storms as well as the prediction of flows at larger scales. Unique to this system are the consistent code styling maintained for the entire model system and thorough internal documentation. Modern software engineering practices are employed to ensure that the system is modular, extensible and easy to use. The system has been undergoing real-time prediction tests at the synoptic through storm scales in the past several years over the continental United States as well as in part of Asia, some of which included retrieved Doppler radar data and hydrometeor types in the initial condition. As the first of a two-part paper series, we describe herein the dynamic and numerical framework of the model, together with the subgrid-scale turbulence and the PBL parameterization. The model dynamic and numerical framework is then verified using idealized and realistic mountain flow cases and an idealized density current. Other physics parameterization schemes will be described in Part II, which is followed by verification against observational data of the coupled soil-vegetation model, surface layer fluxes and the PBL parameterization. Applications of the model to the simulation of an observed supercell storm and to the prediction of a real case are also found in Part II. In the latter case, a long-lasting squall line developed and propagated across the eastern part of the United States following a historical number of tornado outbreak in the state of Arkansas. Received April 14, 2000 Revised July 17, 2000     

Changing Patterns of Population Density in the United States

Changing population density is often ignored in studies of population growth and population transfer in the United States. We show that there is a complex relationship between patterns of population growth and density increase by state. The largest gains in density are in the states of the northeastern megalopolis, California, and Florida. Analysis of the 150 counties with the greatest increases in density between 1980 and 1990 shows that they are well distributed across the United States including the larger metropolitan areas of the “Rustbelt.” In general, the most densely populated states and places are becoming more densely populated, a concept we refer to as densification.